#include "bits/stdc++.h"
using namespace std;
#define FOR(i,j,k) for(int (i)=(j);(i)<(int)(k);++(i))
#define rep(i,j) FOR(i,0,j)
#define each(x,y) for(auto &(x):(y))
#define mp make_pair
#define mt make_tuple
#define all(x) (x).begin(),(x).end()
#define debug(x) cout<<#x<<": "<<(x)<<endl
#define smax(x,y) (x)=max((x),(y))
#define smin(x,y) (x)=min((x),(y))
#define MEM(x,y) memset((x),(y),sizeof (x))
#define sz(x) (int)(x).size()
#define pb push_back
typedef long long ll;
typedef pair<int, int> pii;
typedef vector<int> vi;
typedef vector<ll> vll;

ll K;
int N, sm[51];

ll nex(ll x, ll y) {
    ll z = y / N*sm[N];
    ll l = x%N, r = (x + y) % N;
    if (l < r)z += sm[r] - sm[l];
    if (l > r) {
        z += sm[N] - sm[l] + sm[r];
    }
    return z;
}

bool f(ll x) {
    ll p = 0, q = x, r = 1;
    while (q > 0 && p < K) {
        r = nex(p, q);
        p += q;
        q = r;
    }
    return p >= K;
}

int main(){
    ios::sync_with_stdio(false);
    cin.tie(0);
    string S;
    cin >> N >> K >> S;

    rep(i, N)sm[i + 1] = sm[i] + (S[i] - '0');

    ll l = 0, r = K;
    while (r - l > 1) {
        ll m = (l + r) / 2;
        (f(m) ? r : l) = m;
    }
    cout << r << endl;
}