求问 GESP 6 级 T2

#include<bits/stdc++.h>
using namespace std;
const int N = 500 + 5;
struct Node {
	int a, c;
} node[N];
bool cmp(Node x, Node y) {
	return x.a < y.a;
}
int main() {
	int n, k;
	cin >> n >> k;
	for (int i = 1; i <= n; i++) cin >> node[i].a >> node[i].c;
	sort(node + 1, node + 1 + n, cmp);
	int ans = 0;
	for (int j = n; j >= 1; j--) {
		if (k >= node[j].c) {
			ans += node[j].a;
			k -= node[j].c;
		} else continue;
	}
	cout << ans;
	return 0;
}