#include <iostream>
using namespace std;

int main() {
    int n, k;
    cin >> n >> k;
    int s[n+1];
    int free = 0;
    s[0] = 0;
    for (int i = 1; i <= n; i++) {
        char c;
        cin >> c;
        s[i] = s[i-1] + 1;
        if (free > 0) {
            s[i]--;
            free--;
        }
        free += atoi(&c);
    }
    int ans;
    if (k > n)
        ans = s[n] + max(0,(s[n] - free) * (k / n - 1)) + max(0,s[k%n]-free);
    else
        ans = s[k];
    cout << ans << endl;
    return 0;
}