#include <bits/stdc++.h>

using namespace std;

template <unsigned M_> struct ModInt {
    static constexpr unsigned M = M_;
    unsigned x;
    constexpr ModInt() : x(0) {}
    constexpr ModInt(unsigned x_) : x(x_ % M) {}
    constexpr ModInt(unsigned long long x_) : x(x_ % M) {}
    constexpr ModInt(int x_) : x(((x_ %= static_cast<int>(M)) < 0) ? (x_ + static_cast<int>(M)) : x_) {}
    constexpr ModInt(long long x_) : x(((x_ %= static_cast<long long>(M)) < 0) ? (x_ + static_cast<long long>(M)) : x_) {}
    ModInt &operator+=(const ModInt &a) {
        x = ((x += a.x) >= M) ? (x - M) : x;
        return *this;
    }
    ModInt &operator-=(const ModInt &a) {
        x = ((x -= a.x) >= M) ? (x + M) : x;
        return *this;
    }
    ModInt &operator*=(const ModInt &a) {
        x = (static_cast<unsigned long long>(x) * a.x) % M;
        return *this;
    }
    ModInt &operator/=(const ModInt &a) { return (*this *= a.inv()); }
    ModInt pow(long long e) const {
        if (e < 0)
            return inv().pow(-e);
        ModInt a = *this, b = 1;
        for (; e; e >>= 1) {
            if (e & 1)
                b *= a;
            a *= a;
        }
        return b;
    }
    ModInt inv() const {
        unsigned a = M, b = x;
        int y = 0, z = 1;
        for (; b;) {
            const unsigned q = a / b;
            const unsigned c = a - q * b;
            a = b;
            b = c;
            const int w = y - static_cast<int>(q) * z;
            y = z;
            z = w;
        }
        assert(a == 1);
        return ModInt(y);
    }
    ModInt operator+() const { return *this; }
    ModInt operator-() const {
        ModInt a;
        a.x = x ? (M - x) : 0;
        return a;
    }
    ModInt operator+(const ModInt &a) const { return (ModInt(*this) += a); }
    ModInt operator-(const ModInt &a) const { return (ModInt(*this) -= a); }
    ModInt operator*(const ModInt &a) const { return (ModInt(*this) *= a); }
    ModInt operator/(const ModInt &a) const { return (ModInt(*this) /= a); }
    template <class T> friend ModInt operator+(T a, const ModInt &b) { return (ModInt(a) += b); }
    template <class T> friend ModInt operator-(T a, const ModInt &b) { return (ModInt(a) -= b); }
    template <class T> friend ModInt operator*(T a, const ModInt &b) { return (ModInt(a) *= b); }
    template <class T> friend ModInt operator/(T a, const ModInt &b) { return (ModInt(a) /= b); }
    explicit operator bool() const { return x; }
    bool operator==(const ModInt &a) const { return (x == a.x); }
    bool operator!=(const ModInt &a) const { return (x != a.x); }
    friend std::ostream &operator<<(std::ostream &os, const ModInt &a) { return os << a.x; }
};

mt19937 rng(chrono::steady_clock::now().time_since_epoch().count());
using ll = long long;
// using mint = ModInt<1000000007U>;
using mint = ModInt<998244353U>;

void solve() {
    int n, k;
    cin >> n >> k;
    string s;
    cin >> s;
    k++;
    vector<int> ans;
    vector<int> lens(k);
    vector<int> sum(n / k + 5);
    auto go = [&](auto self, int cur, int total) -> void {
        if (total > n || (n / k + 1) * (k - cur) < n - total) {
            return;
        }
        if (!ans.empty() && cur >= 2) {
            int max_len = *max_element(lens.begin(), lens.end()) > ans.size();
            if (max_len > ans.size())
                return;
            vector<int> msd(2);
            int from = 0;
            for (int i = 0; i < cur; i++) {
                int to = from + lens[i] - 1;
                if (lens[i] == max_len) {
                    msd[0] += s[from] - '0';
                    msd[1] += msd[0] / 10;
                    msd[0] %= 10;
                }
                from = to + 1;
            }
            if (msd[1] && max_len == ans.size())
                return;
            if (max_len + 1 == ans.size() && msd[1] > ans.back())
                return;
        }
        if (cur == k) {
            sum.assign(n / k + 5, 0);
            int from = 0;
            for (int i = 0; i < k; i++) {
                int to = from + lens[i] - 1;
                int r = 0;
                int pos = 0;
                for (int j = to; j >= from; j--) {
                    sum[pos] += s[j] - '0' + r;
                    r = sum[pos] / 10;
                    sum[pos] %= 10;
                    pos++;
                }
                while (r) {
                    sum[pos] += r;
                    r = sum[pos] / 10;
                    sum[pos] %= 10;
                    pos++;
                }
                from = to + 1;
            }
            if (ans.empty()) {
                ans = sum;
                while (ans.back() == 0)
                    ans.pop_back();
            } else {
                for (int j = int(sum.size()) - 1; j >= 0; j--) {
                    if (sum[j] < ans[j]) {
                        ans = sum;
                        while (ans.back() == 0)
                            ans.pop_back();
                        break;
                    } else if (sum[j] > ans[j]) {
                        break;
                    }
                }
            }
            return;
        }
        for (int i = max(1, n / k - 1); i <= min(n / k + 1, ans.empty() ? n : int(ans.size())); i++) {
            lens[cur] = i;
            self(self, cur + 1, total + i);
        }
    };
    go(go, 0, 0);
    reverse(ans.begin(), ans.end());
    for (int d : ans)
        cout << d;
    cout << '\n';
}

int main() {
    ios::sync_with_stdio(false);
    cin.tie(nullptr);
    int T = 1;
    cin >> T;
    for (int tc = 1; tc <= T; tc++) {
        solve();
    }
    return 0;
}