不开启O2优化，提交答案全红；开启O2优化，则是全绿，很懵！想问问各位大神其中区别是什么？代码如下：

#include <stdio.h>
int main(){
    int s1,h1,s2,h2,s3,h3,s4,h4,s5,h5,s6,h6,s7,h7;
    int max=0;
    int n=0;
    int a1,a2,a3,a4,a5,a6,a7;
    scanf("%d %d\n%d %d\n%d %d\n%d %d\n%d %d\n%d %d\n%d %d",&s1,&h1,&s2,&h2,&s3,&h3,&s4,&h4,&s5,&h5,&s6,&s6,&s7,&h7);
    a1=s1+h1;a2=s2+h2;a3=s3+h3;
    a4=s4+h4;a5=s5+h5;a6=s6+h6;
    a7=s7+h7;
    if(a1>max){
            max=a1;
            n=1;
        }
    if(a2>max){
            max=a2;
            n=2;
        }
    if(a3>max){
            max=a3;
            n=3;
        }
    if(a4>max){
            max=a4;
            n=4;
        }
    if(a5>max){
            max=a5;
            n=5;
        } 
    if(a6>max){
            max=a6;
            n=6;
        }
    if(a7>max){
            max=a7;
            n=7;
        }
   if(a1<=8&&a2<=8&&a3<=8&&a4<=8&&a5<=8&&a6<=8&&a7<=8)
        n=0;
    printf("%d",n);
    return 0;
}