#include<bits/stdc++.h>
using namespace std;
using Int = long long;
template<typename T1,typename T2> inline void chmin(T1 &a,T2 b){if(a>b) a=b;}
template<typename T1,typename T2> inline void chmax(T1 &a,T2 b){if(a<b) a=b;}

//INSERT ABOVE HERE
signed main(){
  Int n;
  cin>>n;
  n*=2;
  vector<Int> as(n);
  for(Int i=0;i<n;i++) cin>>as[i];

  vector<Int> dp(n+2),pd(n+2);
  for(Int i=0;i<n;i+=2)
    dp[i+2]=dp[i]+(as[i]-as[i+1]);

  for(Int i=n-2;i>=0;i-=2)
    pd[i]=pd[i+2]+(as[i+1]-as[i]);


  Int ans=-1e18;
  for(Int i=0;i<=n;i+=2)
    chmax(ans,dp[i]+pd[i]);
  cout<<ans<<endl;

  return 0;
}