C++ :

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

const int N = 1000010;
long long a[N],n,k,s,ma;

int main() {
	cin>>n>>k;
	for(int i = 1;i <= n;i++){
		cin>>a[i];
		s = s + a[i];
		a[i] = a[i] + a[i-1];//前缀和	
		//求长度为k的区间和的最大值
		if(i >= k){
			ma = max(ma,a[i]-a[i-k]);
		} 
	} 
	
	cout<<s - ma;
	return 0;
}