40分，请大佬们帮忙看看到底哪里有问题？

代码：

#include <iostream>
using namespace std;

int main()
{
    int n, m, a[3001], min = 301;
    cin >> n >> m;
    for (int i = 0; i < n; i++)
        cin >> a[i];
    for (int i = 0; i < n - m; i++)
    {
        int sum = 0, index = i;
        for (int j = 1; j <= m; j++) sum += a[index++];  // 计算连续 m 个数的值
        if (sum < min) min = sum;
    }
    cout << min << endl;

    return 0;
}