同样的思路，不同输出方式，造成了不同的结果！

//非AC代码 :
#include <iostream>
#include <algorithm>
using namespace std;
#define int long long

const int N = 1e5;
int num[N + 5];
int n, k, ans; 

signed main() {
	cin >> n >> k;
	for (int i = 1; i <= n; i++)
		cin >> num[i];
	sort(num + 1, num + n + 1);
	for (int i = 1; i <= k; i++)
		ans += num[i];
	ans += (k - 1) * k / 2;
	printf("%d", ans);
 	return 0;
}

//AC代码
#include <iostream>
#include <algorithm>
using namespace std;
#define int long long

const int N = 1e5;
int num[N + 5];
int n, k, ans; 

signed main() {
	cin >> n >> k;
	for (int i = 1; i <= n; i++)
		cin >> num[i];
	sort(num + 1, num + n + 1);
	for (int i = 1; i <= k; i++)
		ans += num[i];
	ans += (k - 1) * k / 2;
	cout << ans << endl;
 	return 0;
}

求解释！