记得开 LL、
#include <bits/stdc++.h>
#define ll long long
using namespace std;
ll n, m, k;
ll a[100010];
ll tot;//记录总和
ll sum[100010] = {0};
//记录k项的和
//如果i<=k 直接用前缀和将这一项加进来。
//如果i>k 就有sum[i] = sum[i - 1] + a[i] - a[i - k]; 不停更新数据
ll maxxn = 0;//记录最大值
int main() {
cin >> n >> k;
for (int i = 1; i <= n - 1; i++) {
cin >> a[i];
tot += a[i];
if (i > k) {
sum[i] = sum[i - 1] + a[i] - a[i - k];
} else
sum[i] = sum[i - 1] + a[i];
maxxn = max(maxxn, sum[i]);
}
cout << tot - maxxn;
}