这代码在vs上能运行，怎么到洛谷就编译失败了？？

#include <iostream>
#include <cstdio>
#include <algorithm>
#include <string>
using namespace std;
struct student
{
	string name;
	int y, m, d,num;
}a[110];
int n;
bool cmp(student  a, student  b)
{
	if (a.y != b.y)
		return a.y < b.y;
	if (a.m != b.m)
		return a.m < b.m;
	if (a.d != b.d)
		return a.d < b.d;
	return a.num > b.num;
}
int main(void)
{
	cin >> n;
	for (int i = 1; i <= n; i++)
	{
		cin >> a[i].name >> a[i].y >> a[i].m >> a[i].d;
		a[i].num = i;//第i个人的编号
	}
	sort(a + 1, a + n + 1, cmp);
	for (int i = 1; i <= n; i++)
		cout << a[i].name << endl;
	return 0;
}