#include <iostream>
#include <vector>
#include <string>

using lint = long long;
constexpr lint INF = 1LL << 40;

template <class T>
std::vector<T> vec(int len, T elem) { return std::vector<T>(len, elem); }

void solve() {
    int n;
    lint k;
    std::string s;
    std::cin >> n >> k >> s;

    auto dp = vec(40, vec(n, 0LL));
    for (int i = 0; i < n; ++i) {
        lint get = 0, cnt = 1;
        for (int j = 0; j < n; ++j) {
            ++get;
            cnt += int(s[(i + j) % n] - '0') - 1;
            if (cnt == 0) break;
        }
        dp[0][i] = (cnt > 0 ? INF : get);
    }

    for (int j = 1; j < 40; ++j) {
        for (int i = 0; i < n; ++i) {
            if (dp[j - 1][i] == INF) {
                dp[j][i] = INF;
            } else {
                int ni = (i + dp[j - 1][i]) % n;
                dp[j][i] = std::min(dp[j - 1][i] + dp[j - 1][ni], INF);
            }
        }
    }

    lint ans = 0;
    int i = 0;
    for (int j = 39; j >= 0; --j) {
        if (dp[j][i] > k) continue;
        ans += (1LL << j);
        k -= dp[j][i];
        (i += dp[j][i]) %= n;
    }

    std::cout << ans + (k > 0) << std::endl;
}

int main() {
    std::cin.tie(nullptr);
    std::ios::sync_with_stdio(false);

    solve();

    return 0;
}