#include <bits/stdc++.h>

using namespace std;

#define REP(i,first,last) for (int i=first;i<last;++i)
#define MAX(x,y) (x > y ? x : y)
#define MIN(x,y) (x < y ? x : y)

int N, K;

int main(){
  cin >> N >> K;
  vector<char> ice_box(N);

  REP(i,0,N){
    cin >> ice_box[i];
  }

  int atari = 0;
  int buy = 0;
  int idx = 0;
  int eat = 0;

  while (true) {
    idx %= N;
    if (atari > 0) {
      --atari;
    } else {
      ++buy;
    }
    ++eat;

    atari += ice_box[idx] - '0';
    if (eat + atari >= K) break;

    ++idx;
  }

  cout << buy << endl;
}