#include<stdio.h>
int main()
{
    int n = 0,m = 0,i1 = 0,i2=0,a=0,output = 1000000;
    long long int arr[1002];
    int sum=0;
    scanf("%d %d",&n,&m);
    for (i1 = 0; i1 < n; i1++)
    {
        scanf("%d",&arr[i1]);
    }
    for (i1 = 0; i1+m < n; i1++)
    {
        sum = 0;
        i2 = 0;
        for (a = i1; i2 < m; a++)
        {
            sum = sum+arr[a];
            i2++;
        }
        if (output > sum)
        {
            output = sum;
        }
    }
    printf("%d", output);
    return 0;
}