对样例1输出负数，样例2报错

#include<bits/stdc++.h>
using namespace std;

class student {
public:
    int number;
    int c, m, e;
    int sum;
};

bool cmp(student a, student b) {
    if (a.sum < b.sum) {
        return 1;
    }
    else if (a.sum == b.sum) {
        if (a.c < b.c) {
            return 1;
        }
        if (a.number < b.number) {
            return 1;
        }
    }
    else return 0;
}
int main()
{
    int n;
    student stu[301];
    cin >> n;
    for (int i = 0; i < n; i++) {
        cin >> stu[i].c >> stu[i].m >> stu[i].e;
        stu[i].sum = stu[i].c + stu[i].m + stu[i].e;
    }
    sort(stu, stu + n,cmp);
    for (int i = 0; i < 5; i++) {
        cout << stu[i].number << stu[i].sum << endl;
    }
    return 0;
}