C++ :

#include <cstdio>
int main(){
    int n,m; if(scanf("%d %d",&n,&m)!=2) return 0;
    static char s[100005];
    scanf("%s", s);
    int need=0, wearing=0;
    for(int i=0;i<n;i++){
        if(s[i]=='0'){          // 清洗，所有穿过的衣服洗好可用
            wearing=0;
        }else{
            if(wearing==m) need++;   // 手上可穿的已用完，必须再买
            wearing++;
        }
    }
    printf("%d\n", need);
    return 0;
}