#include<bits/stdc++.h>
using namespace std;
#define int long long
int t,n,m,a[10001],ans;
signed main(){
cin>>t;
while(t--){
cin>>n>>m;
if(n>m){
ans+=n;
}else if(n<m){
ans+=m;
}else if(n==m){
ans+=n;
}
}cout<<ans;
}