#include<cstdio>
#include<iostream>
#include<algorithm>
#include<string>
#include<queue>
#include<vector>
#include<functional>
#include<cmath>
#include<map>
#include<stack>
#include<set>
#include<numeric>
#include<limits>

#define all(x) (x).begin(),(x).end()
#define rall(x) (x).rbegin(),(x).rend()

using namespace std;
typedef long long ll;
typedef pair<int, int> pi;
typedef pair<ll, ll> pl;
typedef pair<ll, string> pls;

int main()
{
	int n;  
	ll k;
	string s;
	cin >> n >> k >> s;
	
	s += s;

	ll num = 1;
	for (int i = 0; i < n*2-1; i++) {
		if (s[i] == '2' && s[i + 1] == '0') {
			s[i + 1] = '1';
		}
	}

	for (int i = 1; i < n; i++) {
		if (s[i - 1] == '0')num++;
	}

	ll ans = 0;
	if (n < k) {
		int buy[110],buy_num=0;
		int nes = (k - n)/n;
		for (int i = n; i < n * 2; i++) {
			if (s[i - 1] == '0') {
				buy[i] = 1;
				buy_num++;
			}
		}

		ans += nes * buy_num;
		for (int i = n; i < (n + (k - n) % n)-1; i++) {
			if (buy[i])ans++;
		}
	}
	else {
		num = 1;
		for (int i = 1; i < n; i++) {
			if (s[i - 1] == '0') {
				num++;
			}
		}
	}
	cout << ans + num << endl;
	return 0;
}