WA on #1

#include <bits/stdc++.h>
using namespace std;
int main(){
    int n;
    cin>>n;
    int a[n],b[n],c[n][2];
    int max_=0,cmax=0;
    for(int i=0;i<n;i++){
        cin>>a[i]>>b[i];
        c[i][0]=max(a[i]-b[i],b[i]);
        c[i][1]=min(a[i]-b[i],b[i]);
        if(c[i][0]>c[max_][0])max_=i;
    }
    for(int i=0;i<n;i++){//找次大值
        if((c[i][0]>c[cmax][0]) && i!=max_)
            cmax=i;
        if(cmax==max_)cmax++;
    }
    cout<<(long long)(c[max_][0]+c[cmax][0]);
    return 0;

}