#include <bits/stdc++.h>
using namespace std;

signed main(){
  int N, K; cin >> N >> K;
  string S; cin >> S;
  vector< int > vis( N );
  for( int i = 0, c = 0, b = 0, e = 0; ; i = ( i + 1 ) % N ){
    if( vis[ i ] ){
      b += ( K - e ) / e * b;
      e += ( K - e ) / e * e;
    }
    vis[ i ] = 1;
    if( e >= K )
      cout << b << endl, exit( 0 );
    ++b, ++e, c += S[ i ] - '0';
    for( int j = ( i + 1 ) % N; ; j = ( j + 1 ) % N ){
      if( c == 0 ){
        i = j - 1;
        break;
      }
      if( i == j )
        cout << b << endl, exit( 0 );
      --c;
      c += S[ j ] - '0';
      ++e;
    }
    if( e >= K )
      cout << b << endl, exit( 0 );
  }
  return 0;
}