#include <bits/stdc++.h>
using ll = long long int;
using namespace std;
ll mod=1e9+7;
       

int main(){
  int n;
  cin >> n;
  int a[n*2];
  ll anss=0;
  ll ans=0;
  for(int i=0;i<n*2;i++){cin >> a[i];
  if((i+2)%2==0){anss+=a[i];}else{anss-=a[i];}}
  ans=anss;
  for(int i=n-1;i>=0;i--){
    anss+=a[2*i+1]*2;
    anss-=a[2*i]*2;
    ans=max(ans,anss);
  }
  cout << ans << endl;
}