#include <stdio.h>
int main()
{
    int n ,m, sum, min = 100;
    scanf("%d %d",&n,&m);
    int a[3001];
    for (int i = 0; i < n; i++)
    {
        scanf("%d",&a[i]);
    }
    //输入
    for (int j = 0; j <= n-m; j++)
    {
        sum = 0;
        for (int k = 0; k < m; k++)
        {
            sum += a[j+k];
        } 
        if(sum<min)
        min = sum;
    }  
    //
    printf("%d",min);
}