#include <bits/stdc++.h>

using namespace std;

#define FOR(i,a,b) for(int i=(a);i<(b);i++)
#define REP(i,n) FOR(i,0,n)
#define ALL(v) (v).begin(),(v).end()

template<typename A, typename B> inline bool chmax(A &a, B b) { if (a<b) { a=b; return 1; } return 0; }
template<typename A, typename B> inline bool chmin(A &a, B b) { if (a>b) { a=b; return 1; } return 0; }

typedef unsigned long long ull;
typedef long long ll;
typedef pair<int, int> pii;
typedef pair<ll, ll> pll;
typedef pair<int, pii> P;

const ll INF = 1ll<<29;
const ll MOD = 1000000007;
const double EPS  = 1e-10;

int main() {
	ll n, k;
	string s;
	cin >> n >> k >> s;
	
	ll buycnt = 0, now = 0;
	ll memo[51] = {};
	
	REP(i, s.size()) {
		if (!now) buycnt++;
		else now--;
		
		now += s[i] - '0';
		
		memo[i + 1] = buycnt;
	}
	
	ll ans = 0;
	
	if (k <= n) ans = memo[k];
	else {
		k -= n;
		ans += buycnt;
		
		if (now < buycnt) {
			ll tmp = k / n;
			ans += (buycnt - now) * tmp;
			
			k %= n;
			
			ans += max(0ll, memo[k] - now);
		}
	}
	
	cout << ans << endl;
	
	
	
	return 0;
}