为什么这段代码我获得了70分却不是100分

#include <iostream>
#include <algorithm>

using namespace std;

struct ps{
    int id;
    int chi;
    int mat;
    int eng;
    int sum;
};

bool my_cmp(ps x,ps y){
    if (x.sum==y.sum)
    {
        if (x.chi==x.chi)
            return x.id<y.id;
        else
            return x.chi>y.chi;
    }
    else
        return x.sum>y.sum;
}

ps a[10001]; 

int main(){
    int n,i;
    cin>>n;
    for (i=0;i<n;i++)
    {
        a[i].id=i+1;
        cin>>a[i].chi>>a[i].mat>>a[i].eng;
        a[i].sum=a[i].chi+a[i].mat+a[i].eng; 
    }
    sort (a,a+n,my_cmp);
    for (i=0;i<5;i++)
    {
        cout<<a[i].id<<" "<<a[i].sum<<endl;
    }
    return 0;
}