#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
template<class T>bool chmax(T &a, const T &b) { if (a<b) { a=b; return true; } return false; }
template<class T>bool chmin(T &a, const T &b) { if (b<a) { a=b; return true; } return false; }
#define all(x) (x).begin(),(x).end()
#define fi first
#define se second
#define mp make_pair
#define si(x) int(x.size())
const int mod=998244353,MAX=300005,INF=1<<30;

// 文字列

// from: https://gist.github.com/yosupo06/ddd51afb727600fd95d9d8ad6c3c80c9
// (based on AtCoder STL)


namespace atcoder {
    
    namespace internal {
        
        std::vector<int> sa_naive(const std::vector<int>& s) {
            int n = int(s.size());
            std::vector<int> sa(n);
            std::iota(sa.begin(), sa.end(), 0);
            std::sort(sa.begin(), sa.end(), [&](int l, int r) {
                if (l == r) return false;
                while (l < n && r < n) {
                    if (s[l] != s[r]) return s[l] < s[r];
                    l++;
                    r++;
                }
                return l == n;
            });
            return sa;
        }
        
        std::vector<int> sa_doubling(const std::vector<int>& s) {
            int n = int(s.size());
            std::vector<int> sa(n), rnk = s, tmp(n);
            std::iota(sa.begin(), sa.end(), 0);
            for (int k = 1; k < n; k *= 2) {
                auto cmp = [&](int x, int y) {
                    if (rnk[x] != rnk[y]) return rnk[x] < rnk[y];
                    int rx = x + k < n ? rnk[x + k] : -1;
                    int ry = y + k < n ? rnk[y + k] : -1;
                    return rx < ry;
                };
                std::sort(sa.begin(), sa.end(), cmp);
                tmp[sa[0]] = 0;
                for (int i = 1; i < n; i++) {
                    tmp[sa[i]] = tmp[sa[i - 1]] + (cmp(sa[i - 1], sa[i]) ? 1 : 0);
                }
                std::swap(tmp, rnk);
            }
            return sa;
        }
        
        template <int THRESHOLD_NAIVE = 10, int THRESHOLD_DOUBLING = 40>
        std::vector<int> sa_is(const std::vector<int>& s, int upper) {
            int n = int(s.size());
            if (n == 0) return {};
            if (n == 1) return {0};
            if (n == 2) {
                if (s[0] < s[1]) {
                    return {0, 1};
                } else {
                    return {1, 0};
                }
            }
            if (n < THRESHOLD_NAIVE) {
                return sa_naive(s);
            }
            if (n < THRESHOLD_DOUBLING) {
                return sa_doubling(s);
            }
            
            std::vector<int> sa(n);
            std::vector<bool> ls(n);
            for (int i = n - 2; i >= 0; i--) {
                ls[i] = (s[i] == s[i + 1]) ? ls[i + 1] : (s[i] < s[i + 1]);
            }
            std::vector<int> sum_l(upper + 1), sum_s(upper + 1);
            for (int i = 0; i < n; i++) {
                if (!ls[i]) {
                    sum_s[s[i]]++;
                } else {
                    sum_l[s[i] + 1]++;
                }
            }
            for (int i = 0; i <= upper; i++) {
                sum_s[i] += sum_l[i];
                if (i < upper) sum_l[i + 1] += sum_s[i];
            }
            
            auto induce = [&](const std::vector<int>& lms) {
                std::fill(sa.begin(), sa.end(), -1);
                std::vector<int> buf(upper + 1);
                std::copy(sum_s.begin(), sum_s.end(), buf.begin());
                for (auto d : lms) {
                    if (d == n) continue;
                    sa[buf[s[d]]++] = d;
                }
                std::copy(sum_l.begin(), sum_l.end(), buf.begin());
                sa[buf[s[n - 1]]++] = n - 1;
                for (int i = 0; i < n; i++) {
                    int v = sa[i];
                    if (v >= 1 && !ls[v - 1]) {
                        sa[buf[s[v - 1]]++] = v - 1;
                    }
                }
                std::copy(sum_l.begin(), sum_l.end(), buf.begin());
                for (int i = n - 1; i >= 0; i--) {
                    int v = sa[i];
                    if (v >= 1 && ls[v - 1]) {
                        sa[--buf[s[v - 1] + 1]] = v - 1;
                    }
                }
            };
            
            std::vector<int> lms_map(n + 1, -1);
            int m = 0;
            for (int i = 1; i < n; i++) {
                if (!ls[i - 1] && ls[i]) {
                    lms_map[i] = m++;
                }
            }
            std::vector<int> lms;
            lms.reserve(m);
            for (int i = 1; i < n; i++) {
                if (!ls[i - 1] && ls[i]) {
                    lms.push_back(i);
                }
            }
            
            induce(lms);
            
            if (m) {
                std::vector<int> sorted_lms;
                sorted_lms.reserve(m);
                for (int v : sa) {
                    if (lms_map[v] != -1) sorted_lms.push_back(v);
                }
                std::vector<int> rec_s(m);
                int rec_upper = 0;
                rec_s[lms_map[sorted_lms[0]]] = 0;
                for (int i = 1; i < m; i++) {
                    int l = sorted_lms[i - 1], r = sorted_lms[i];
                    int end_l = (lms_map[l] + 1 < m) ? lms[lms_map[l] + 1] : n;
                    int end_r = (lms_map[r] + 1 < m) ? lms[lms_map[r] + 1] : n;
                    bool same = true;
                    if (end_l - l != end_r - r) {
                        same = false;
                    } else {
                        while (l < end_l) {
                            if (s[l] != s[r]) {
                                break;
                            }
                            l++;
                            r++;
                        }
                        if (l == n || s[l] != s[r]) same = false;
                    }
                    if (!same) rec_upper++;
                    rec_s[lms_map[sorted_lms[i]]] = rec_upper;
                }
                
                auto rec_sa =
                sa_is<THRESHOLD_NAIVE, THRESHOLD_DOUBLING>(rec_s, rec_upper);
                
                for (int i = 0; i < m; i++) {
                    sorted_lms[i] = lms[rec_sa[i]];
                }
                induce(sorted_lms);
            }
            return sa;
        }
        
    }  // namespace internal
    
    std::vector<int> suffix_array(const std::vector<int>& s, int upper) {
        assert(0 <= upper);
        for (int d : s) {
            assert(0 <= d && d <= upper);
        }
        auto sa = internal::sa_is(s, upper);
        return sa;
    }
    
    template <class T> std::vector<int> suffix_array(const std::vector<T>& s) {
        int n = int(s.size());
        std::vector<int> idx(n);
        iota(idx.begin(), idx.end(), 0);
        sort(idx.begin(), idx.end(), [&](int l, int r) { return s[l] < s[r]; });
        std::vector<int> s2(n);
        int now = 0;
        for (int i = 0; i < n; i++) {
            if (i && s[idx[i - 1]] != s[idx[i]]) now++;
            s2[idx[i]] = now;
        }
        return internal::sa_is(s2, now);
    }
    
    std::vector<int> suffix_array(const std::string& s) {
        int n = int(s.size());
        std::vector<int> s2(n);
        for (int i = 0; i < n; i++) {
            s2[i] = s[i];
        }
        return internal::sa_is(s2, 255);
    }
    
    template <class T>
    std::vector<int> lcp_array(const std::vector<T>& s,
                               const std::vector<int>& sa) {
        int n = int(s.size());
        assert(n >= 1);
        std::vector<int> rnk(n);
        for (int i = 0; i < n; i++) {
            rnk[sa[i]] = i;
        }
        std::vector<int> lcp(n - 1);
        int h = 0;
        for (int i = 0; i < n; i++) {
            if (h > 0) h--;
            if (rnk[i] == 0) continue;
            int j = sa[rnk[i] - 1];
            for (; j + h < n && i + h < n; h++) {
                if (s[j + h] != s[i + h]) break;
            }
            lcp[rnk[i] - 1] = h;
        }
        return lcp;
    }
    
    std::vector<int> lcp_array(const std::string& s, const std::vector<int>& sa) {
        int n = int(s.size());
        std::vector<int> s2(n);
        for (int i = 0; i < n; i++) {
            s2[i] = s[i];
        }
        return lcp_array(s2, sa);
    }
    
    template <class T> std::vector<int> z_algorithm(const std::vector<T>& s) {
        int n = int(s.size());
        if (n == 0) return {};
        std::vector<int> z(n);
        z[0] = 0;
        for (int i = 1, j = 0; i < n; i++) {
            int& k = z[i];
            k = (j + z[j] <= i) ? 0 : std::min(j + z[j] - i, z[i - j]);
            while (i + k < n && s[k] == s[i + k]) k++;
            if (j + z[j] < i + z[i]) j = i;
        }
        z[0] = n;
        return z;
    }
    
    std::vector<int> z_algorithm(const std::string& s) {
        int n = int(s.size());
        std::vector<int> s2(n);
        for (int i = 0; i < n; i++) {
            s2[i] = s[i];
        }
        return z_algorithm(s2);
    }
    
}  // namespace atcoder

template<typename T>
struct SparseTable{
    using F=function<T(T,T)>;
    
    int n,logn;
    vector<vector<T>> dat;
    vector<int> loglen;
    F f;
    T ti;
    
    SparseTable(int n_,F f,T ti) :f(f),ti(ti){
        n=1;
        logn=1;
        while(n<n_){
            n*=2;
            logn++;
        }
        loglen.resize(n+3);
        n=n_;
        int j=0;
        for(int i=1;i<n+3;i++){
            loglen[i]=j;
            if(i+1>(1<<(j+1))) j++;
        }
        
        dat.resize(logn);
        
        for(int i=0;i<logn;i++){
            dat[i].assign(n+1,ti);
        }
    }
    
    void set(vector<T> &v){
        for(int j=0;j<n+1;j++){
            if(j<si(v)) dat[0][j]=v[j];
        }
    }
    
    void set(int j,T x){
        dat[0][j]=x;
    }
    
    void built(){
        for(int i=1;i<logn;i++){
            for(int j=0;j<n+1;j++){
                T vl=dat[i-1][j],vr;
                if(j+(1<<(i-1))>=n+1) vr=ti;
                else vr=dat[i-1][j+(1<<(i-1))];
                dat[i][j]=f(vl,vr);
            }
        }
    }
    
    T query(int l,int r){
        if(l>=r) swap(l,r);
        if(l==r) return ti;
        T vl=dat[loglen[r-l]][l],vr=dat[loglen[r-l]][r-(1<<loglen[r-l])];
        return f(vl,vr);
    }
};


int main(){
    
    std::ifstream in("text.txt");
    std::cin.rdbuf(in.rdbuf());
    cin.tie(0);
    ios::sync_with_stdio(false);
    
    int Q;cin>>Q;
    while(Q--){
        int N,K;cin>>N>>K;
        string S;cin>>S;
        if(N<=K){
            cout<<N+K<<"\n";
            continue;
        }
        
        string T;
        T+=S;
        T+='$';
        reverse(all(S));
        T+=S;
        reverse(all(S));
        
        auto sa=atcoder::suffix_array(T);
        auto lcp=atcoder::lcp_array(T,sa);
        SparseTable<int> spa(si(lcp),[](int a,int b){
            return min(a,b);
        },INF);
        for(int i=0;i<si(lcp);i++) spa.set(i,lcp[i]);
        spa.built();
        
        vector<int> A(N),B(N);
        for(int i=0;i<si(sa);i++){
            if(sa[i]<N){
                A[sa[i]]=i;
            }else if(sa[i]>N){
                B[N-1-(sa[i]-(N+1))]=i;
            }
        }
        
        int ans=K+K;
        for(int c=0;c<N;c++){
            int len=spa.query(A[c],B[c]);
            chmax(ans,len*2-1+K);
            for(int k=1;k<=K;k++){
                int L=c-len,R=c+len+k;
                if(R>N) break;
                int ad=0;
                if(L>=0&&R<N){
                    ad=spa.query(A[R],B[L])*2;
                }
                chmax(ans,len*2-1+k+k+ad);
            }
            for(int k=1;k<=K;k++){
                int L=c-len-k,R=c+len;
                if(L<-1) break;
                int ad=0;
                if(L>=0&&R<N){
                    ad=spa.query(A[R],B[L])*2;
                }
                chmax(ans,len*2-1+k+k+ad);
            }
        }
        for(int c=0;c+1<N;c++){
            int len=spa.query(A[c+1],B[c]);
            chmax(ans,len*2+K);
            for(int k=1;k<=K;k++){
                int L=c-len,R=c+1+len+k;
                if(R>N) break;
                int ad=0;
                if(L>=0&&R<N){
                    ad=spa.query(A[R],B[L])*2;
                }
                chmax(ans,len*2+k+k+ad);
            }
            for(int k=1;k<=K;k++){
                int L=c-len-k,R=c+1+len;
                if(L<-1) break;
                int ad=0;
                if(L>=0&&R<N){
                    ad=spa.query(A[R],B[L])*2;
                }
                chmax(ans,len*2+k+k+ad);
            }
        }
        cout<<ans<<endl;
    }
}