https://www.acmicpc.net/problem/2217
#include <iostream>
#include<algorithm>
#include<vector>
using namespace std;
int main() {
int N;
cin >> N;
vector <int>v;
for (int i = 0; i < N; i++) {
//배열에 넣어줌
scanf("%d", &v[i]);
}
//오름 차순 정렬
sort(v.begin(), v.end());
int ans = 0;
//이부분이 이해 안됨... 왜 즤....감쟈...
for (int i = 0; i < N; i++) {
ans = max(ans, v[i] * (N- i));
}
return 0;
}