#include <iostream>
#include <string>
#include <sstream>
using namespace std;
int to_int(char tmp){
        int integer;
        string t="";t+=tmp;
        istringstream to(t);
        to>>integer;
        return integer;
}
int main(){
        int N,K;
        string str;
        cin >> N >>K;
        cin >> str;
        long long int counter=0;
        int hit=0;
        int i=0;
        while(K>0){
                int tmp=to_int(str[i]);
                if(hit==0 )counter++;
                else hit--;
                hit+=tmp;
                K--;
                i=(i+1)%N;
        }
        cout << counter << endl;
        return 0;
}