#include <iostream>
typedef long long int ll;
using namespace std;

int buy_ice(int k, int *box){
    int cost = 0;
    int free = 0;
    for (int i = 0; i < k; i++){
        int ice = box[i];
        if (free > 0){
            free -= 1;
        } else {
            cost += 1;
        }
        if (ice == 2){
            free += 2;
        } else if (ice == 1){
            free += 1;
        } 
    }
    return cost;
}

int main(){
    ll n, k;
    cin >> n >> k;
    int box[k];
    string ices;
    cin >> ices;
    for (int i = 0; i < n; i++){
        int ice = ices[i] - '0';
        for (int j = 0; i + (n * j) < k; j++){
            box[i + (n * j)] = ice;
        }
    }
    for (int i = 0; i < k; i++){
    }
    int cost = buy_ice(k % n, box);
    cout << cost << endl;
    
    return 0;
}