#include <stdio.h>

long n, z, s, poz, min = 10000000;
int k;
char sir[100009];
//FILE *f;

int main ()
{
    long i, j;

    //f = fopen("buffer.in","r");
    scanf("%ld %d",&n,&k);
    if((long)k > n) printf("0\n");
    else {
         scanf("%c",&sir[0]);
         for(i=1; i<=n; i++)
        {
        scanf("%c",&sir[i]);
        if(sir[i] == '\n')
          i--;
        }
         for(i=1; i<=k; i++)
        {
        z--;
        if(sir[i] == '*')
          {
          s += 10;
          z = k;
          }
        else s += sir[i] - '0';
        }
        if(z <= 0 && s < min)
          {
          min = s;
          poz = i-k;
          }
         for(; i<=n; i++)
        {
        if(sir[i-k] == '*')
          s -= 10;
        else s -= sir[i-k] - '0';
        z--;
        if(sir[i] == '*')
          {
          s += 10;
          z = k;
          }
        else s += sir[i] - '0';
        if(z <= 0 && s < min)
          {
          min = s;
          poz = i-k+1;
          }
        }
         }
    printf("%ld\n",poz);
    return 0;
}