#include<bits/stdc++.h>
using namespace std;

int main (){
    int n,m;
    int v[1000];
    int result=INT_MAX;
    
    cin >> n >> m ;
    for(int i=0;i<n;i++){

        cin >> v[i];
    }
    int it = n-m+1;
    for(int j=0;j<it;j++){
        int j2=j;
        int temp = 0;
        for(int k=0;k<m;k++){
            temp += v[j2++];
        }
        if(temp < result) result = temp;
    }

        cout << result;

    system("pause");
    return 0;
}