// includes
#include <bits/stdc++.h>

// macros
#define ll long long int
#define pb emplace_back
#define mk make_pair
#define pq priority_queue
#define FOR(i, a, b) for(int i=(a);i<(b);++i)
#define rep(i, n) FOR(i, 0, n)
#define rrep(i, n) for(int i=((int)(n)-1);i>=0;i--)
#define all(x) (x).begin(),(x).end()
#define sz(x) ((int)(x).size())
#define UNIQUE(v) v.erase(unique(v.begin(), v.end()), v.end())
#define FI first
#define SE second
using namespace std;

//  types
typedef pair<int, int> P;
typedef pair<ll, int> Pl;
typedef pair<ll, ll> Pll;
typedef pair<double, double> Pd;
 
// constants
const int inf = 1e9;
const ll linf = 1LL << 50;
const double EPS = 1e-10;
const int mod = 1e9 + 7;

// solve
template <class T>bool chmax(T &a, const T &b){if(a < b){a = b; return 1;} return 0;}
template <class T>bool chmin(T &a, const T &b){if(a > b){a = b; return 1;} return 0;}
template <typename T> istream &operator>>(istream &is, vector<T> &vec){for(auto &v: vec)is >> v; return is;}

ll A[101][41], B[101][41];

int main(int argc, char const* argv[])
{
  ios_base::sync_with_stdio(false);
  cin.tie(0);
  int n;
  ll k;
  cin >> n >> k;
  string s;
  cin >> s;
  for(int i = 0; i < 101; i++){
    int cnt = 0;
    int curr = i;
    for(int j = 0; j < n; j++){
      if(curr == 0){
        cnt++;
      }else{
        curr--;
      }
      curr += int(s[j] - '0');
    }
    A[i][0] = min(curr, 2 * n);
    B[i][0] = cnt;
  }
  for(int i = 1; i < 41; i++){
    for(int j = 0; j < 101; j++){
      A[j][i] = A[A[j][i-1]][i-1];
      B[j][i] = B[j][i-1] + B[A[j][i-1]][i-1];
    }
  }
  ll K = k / n;
  ll res = 0;
  int curr = 0;
  int cnt = 0;
  while(K){
    if(K % 2 == 1){
      res += B[curr][cnt];
      curr = A[curr][cnt];
    }
    cnt++;
    K /= 2;
  }
  for(int j = 0; j < k % n; j++){
    if(curr == 0){
      res++;
    }else{
      curr--;
    }
    curr += int(s[j] - '0');
  }
  cout << res << endl;
	return 0;
}