代码第7个点RE，求助大佬```cpp
#include<bits/stdc++.h>
using namespace std;
typedef long long ll;
struct Node{
ll x,y,s;
}a[500005];
ll ans=0;
int n;
bool cmp(Node xx,Node yy){
return xx.s<yy.s;
}
int main(){
scanf("%d",&n);
for(int i=1;i<=n;i++){
scanf("%lld%lld",&a[i].x,&a[i].y);
a[i].s=a[i].x+a[i].y;
}
sort(a+1,a+1+n,cmp);
for(int i=1;i<=n/2;i++){
ans+=min(a[i].x,a[i].y);
}
for(int i=n/2+1;i<=n;i++){
ans-=max(a[i].x,a[i].y);
}
printf("%lld",ans);
return 0;
}
