#include <iostream>
#include <cstring>
using namespace std;

#define int unsigned long long

const int MAX_N = 60;

int n, k;
string s;

bool visited[MAX_N];
int memo[MAX_N];

bool f(int);
bool rec(int, int, int);

bool f(int x) {
    memset(visited, false, sizeof(visited));
    memset(memo, 0, sizeof(memo));
    return rec(0, x, 0);
}

bool rec(int ice_i, int available_num, int accum) {
    if (accum >= k) {
        return true;
    } else if (available_num == 0) {
        return false;
    } else if (visited[ice_i]) {
        if (memo[ice_i] <= available_num) return true;
        else {
            int dec = memo[ice_i] - available_num;
            // n * (memo[ice_i] / dec)分だけ使える
            memset(visited, false, sizeof(visited));
            memset(memo, 0, sizeof(memo));
            return rec(ice_i, available_num % dec, accum + n * (available_num / dec));
        }
    } else {
        visited[ice_i] = true;
        memo[ice_i] = available_num;
        return rec((ice_i + 1) % n, available_num + s[ice_i] - '1', accum + 1);
    }
}

signed main() {
    cin >> n >> k;
    cin >> s;

    int lb = 0, ub = k;
    while (ub - lb > 1) {
        int mid = (lb + ub) / 2;
        if (f(mid)) {
            ub = mid;
        } else {
            lb = mid;
        }
    }
    cout << ub << endl;

    return 0;
}