#include<bits/stdc++.h>

using namespace std;

typedef long long LL;
#define N 30'0000

void output(vector<LL> &f){
    for (auto x:f) cout<<x<<' '; cout<<endl;
}
const valarray<LL> B={233,199},mod={998244353,(LL)1e9+7};
valarray<LL> pw[N];
struct hashstring{
    vector<valarray<LL>> f;
    void build(string s){
        f.resize(s.size()+1);
        f[0]={0,0};
        for (LL i=0;i<s.size();++i){
            auto w=s[i];
            f[i+1]=(f[i]*B+w)%mod;
        }
    }
    valarray<LL> calc(LL i,LL len){
        return (f[i+len]-f[i]*pw[len]%mod+mod)%mod;
    }
};
void init(LL n){
    pw[0]={1,1}; for (LL i=1;i<=n;++i) pw[i]=pw[i-1]*B%mod;
}

bool operator == (const valarray<LL> &a,const valarray<LL> &b){
    if (a.size()!=b.size()) return false;
    for (LL i=0;i<a.size();++i){
        if (a[i]!=b[i]) return false;
    }
    return true;
}

string rand_string(){
    LL len=rand()%10+1;
    string st(len,'a');
    for (auto &x:st) x=rand()%2+'a';
    // cerr<<st<<endl;
    return st;
}

void solve(){
    LL n,m; cin>>n>>m;
    vector<string> s(n);
    vector<hashstring> f(n);
    for (LL i=0;i<n;++i){
        cin>>s[i];
        f[i].build(s[i]);
    }
    vector<vector<LL>> lyndon(n),sim(n);
    vector<LL> ans(n);
    for (LL i=0;i<n;++i){
        auto st=s[i]+'0';
        for (LL lst=-1,cyc=1,j=1;j<st.size();++j){
            if (st[j]>st[j-cyc]) cyc=j-lst;
            else{
                if (st[j]<st[j-cyc]){
                    ans[i]=max(ans[i],cyc);
                    if (j==st.size()-1){
                        sim[i].push_back(lst+1);
                    }
                    for (lst+=cyc;lst<j;lst+=cyc){
                        lyndon[i].push_back(lst);
                    }
                    lst-=cyc;
                    cyc=1;
                    j=lst+1;
                }
            }
        }
    }
    auto calc=[&](LL i,LL j,LL p,LL len)->valarray<LL>
    {
        if (p+len<=s[i].size()) return f[i].calc(p,len);
        if (p>=s[i].size()) return f[j].calc(p-s[i].size(),len);
        LL t=s[i].size()-p;
        return (f[i].calc(p,t)*pw[len-t]+f[j].calc(0,len-t))%mod;
    };
    auto check=[&](LL i,LL j,LL p1,LL p2,LL len){
        if (calc(i,j,p1,len)==calc(i,j,p2,len)) return false;
        LL l=1,r=len,k=0;
        while (l<=r){
            LL mid=(l+r)>>1;
            if (calc(i,j,p1,mid)==calc(i,j,p2,mid)){
                k=mid;
                l=mid+1;
            }
            else{
                r=mid-1;
            }
        }
        auto c1=(p1+k<s[i].size())?s[i][p1+k]:s[j][p1+k-s[i].size()];
        auto c2=(p2+k<s[i].size())?s[i][p2+k]:s[j][p2+k-s[i].size()];
        return c1<c2;
    };
    auto max_lyndon=[&](string st){
        st=st+'0';
        LL ret=0;
        for (LL lst=-1,cyc=1,j=1;j<st.size();++j){
            if (st[j]>st[j-cyc]) cyc=j-lst;
            else{
                if (st[j]<st[j-cyc]){
                    ret=max(ret,cyc);
                    for (lst+=cyc;lst<j;lst+=cyc);
                    lst-=cyc;
                    cyc=1;
                    j=lst+1;
                }
            }
        }
        return ret;
    };
    while (m--){
        LL i,j; cin>>i>>j; --i; --j;
        LL tmp=max(ans[i],ans[j]);
        LL t=sim[i].back();
        for (LL k=0;k+1<sim[i].size();++k){
            LL l=1,r=s[j].size();
            LL p1=sim[i][k];
            LL p2=sim[i][k+1];
            LL len0=s[i].size()-p2,mx=0;
            if (check(i,j,p1,p2,len0+s[j].size())){
                t=sim[i][k];
                break;
            }
        }
        if (check(i,j,t,s[i].size(),s[j].size())){
            LL l=0,r=lyndon[j].size()-1,pre=0;
            while (l<=r){
                LL mid=(l+r)>>1;
                LL L=mid==0?0:lyndon[j][mid-1]+1;
                LL R=lyndon[j][mid];
                if (check(i,j,t,s[i].size()+L,R-L+1)){
                    pre=lyndon[j][mid]+1;
                    l=mid+1;
                }
                else{
                    r=mid-1;
                }
            }
            tmp=max(tmp,(LL)s[i].size()-t+pre);
        }
        // assert(tmp==max_lyndon(s[i]+s[j]));
        cout<<tmp<<'\n';
    }
}
int main(){
    srand((unsigned long long)new char+time(0));
    ios::sync_with_stdio(0); cin.tie(0);
    LL T; cin>>T;
    init(200000);
    while (T--) solve();
}