为神马我的总是50分！C语言师兄师姐们看一下

#include<stdio.h>
struct student
{
    int num;
    int yuwen;
    int shuxue;
    int yingyu;
    int sum;
}a[100],temp;
int main()
{
    int n,i,j;
    scanf("%d",&n);
    for(i=1;i<=n;i++)
    scanf("%d %d %d",&a[i].yuwen,&a[i].shuxue,&a[i].yingyu);
    for(i=1;i<=n;i++)
{
    a[i].num=i;
    a[i].sum=a[i].yuwen+a[i].shuxue+a[i].yingyu;
}
    for(j=1;j<=n-1;j++)
    for(i=1;i<=n;i++)
{
    if(a[i].sum<a[i+1].sum)
{
    temp=a[i];
    a[i]=a[i+1];
    a[i+1]=temp;
}
    if(a[i].sum==a[i+1].sum)
    if(a[i].num<a[i+1].num)
{
    temp=a[i];
    a[i]=a[i+1];
    a[i+1]=temp;
}
}
    for(i=1;i<=5;i++)
    printf("%d %d\n",a[i].num,a[i].sum);
    return 0;
}