一种：

#include<iostream>
#include<cstdio>
using namespace std;
struct jj{
	int day,a,b,c;
}a_week[8];
int main(){
	int ans=0,maxx=0;
	for(int i=1;i<=7;i++){
		a_week[i].day=i;
		scanf("%d%d",&a_week[i].a,&a_week[i].b);
		a_week[i].c=a_week[i].a+a_week[i].b;
	}
	for(int i=1;i<=7;i++){
		if(a_week[i].c>=8&&a_week[i].c>maxx){
			maxx=a_week[i].c;
			ans=a_week[i].day;
		}
	}
	printf("%d",ans);
	return 0;
}

还有一种：

#include<iostream>
#include<cstdio>
using namespace std;
struct jj{
	int day,a,b,c;
}a_week[8];
int main(){
	int ans=0,maxx=0;
	for(int i=1;i<=7;i++){
		a_week[i].day=i;
		scanf("%d%d",&a_week[i].a,&a_week[i].b);
		a_week[i].c=a_week[i].a+a_week[i].b;
	}
	for(int i=1;i<=7;i++){
		if(a_week[i].c>maxx){
			maxx=a_week[i].c;
			ans=a_week[i].day;
		}
	}
	if(maxx<8)printf("0");
	else printf("%d",ans);
	return 0;
}