这个比较函数有什么问题吗？为什么WA了啊

#include <algorithm>
#include <bits/stdc++.h>
using namespace std;
struct stu{
    string name;
    int year;
    int month;
    int day;
}a[105];
bool cmp(stu a,stu b)
{
    if(a.year > b.year)
        return true;
    else if(a.year == b.year && a.month > b.month)
        return true;
    else if(a.month == b.month && a.day > b.day)
        return true;
    else
        return false;;
}
int main()
{
    int n;cin >> n;
    for(int i = 1;i <= n;i++)
        cin >> a[i].name >> a[i].year >> a[i].month >> a[i].day;
    sort(a+1,a+1+n,cmp);
    for(int i = n;i >= 1;i--)
        cout << a[i].name << endl;
}