#include <stdio.h>
long long a[1000];
int main(){
   
    int n, m;
  long long min = 300000000000;
    scanf("%d %d", &n, &m);
   

    for (int i = 1; i <= n; i++) { scanf("%lld", &a[i]);  }
    if (m != 0) {
        
            for (int i = 1; i <= n - m; i++) {
                int j = i;
                long long sum = 0;
                while (j < i + m) {
                    sum += a[j];
                    j++;
                }
                if (sum < min)min = sum;
            }
            printf("%lld", min);
        
      
    }
    else printf("0");
    return 0;

}