#include <cstdio>
#include <algorithm>

int main(){
    int N, K;
    scanf("%d %d", &N, &K);

    char ice[100];
    scanf("%s", ice);

    for(int i=N;i<2*N;i++){ice[i] = ice[i-N];}

    bool bought[100];
    std::fill(bought, bought+2*N, false);
    int cost[100], last = 0;
    std::fill(cost, cost+2*N, 0);
    
    for(int i=0;i<2*N;i++){
        if(!bought[i]){
            cost[i] = 1;
        }
        
        if(ice[i] == '1'){
            if(last+1 < 2*N){bought[last+1] = true; last += 1;}
        }else if(ice[i] == '2'){
            if(last+1 < 2*N){bought[last+1] = true; last += 1;}
            if(last+1 < 2*N){bought[last+1] = true; last += 1;}
        }

        last = std::max(i+1, last);
    }

    for(int i=1;i<N;i++){
        cost[i] += cost[i-1];
        cost[i+N] += cost[i-1+N];
    }

    // for(int i=0;i<2*N;i++){
    //     printf("%d: %d\n", i, cost[i]);
    // }

    int res;
    if(K <= N){
        res = cost[K-1];
    }else{
        res = cost[N-1];
        K -= N;
        while(K >= N){
            res += cost[2*N-1];
            K -= N;
        }
        res += K>0?cost[K-1+N]:0;
    }

    printf("%d\n", res);
}