UnAccepted 80, #8 #10错了, confused... code:

#include <algorithm>
#include <iostream>
#include <stdio.h>
#include <string.h>
using namespace std;

int main() {
    int n, m, sum;
    long long min = 2e+18;
    cin >> n >> m;
    int a[n];
    for (int i = 0; i < n; i ++) {
        cin >> a[i];
    }
    for (int i = 0; i < n - m; i ++) {
        sum = 0;
        for (int j = 0; j < m; j ++) {
            sum += a[i + j];
        }
        if (sum < min) {
            min = sum;
        }
    }
    cout << min;
    return 0;
}

各位大佬帮帮蒟蒻, PLS PLS PLS PLS!!
$ygg\ pls$
(验证码fkx4)