#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
#define pb push_back
#define fi first
#define se second
typedef pair<ll,ll> P;
using VP = vector<P>; using VVP = vector<VP>;
using VI = vector<ll>; using VVI = vector<VI>; using VVVI = vector<VVI>;
const int inf=1e9+7;
const ll INF=1LL<<61;
const ll mod=1e9+7;

template<class T>
inline bool chmax(T &a, T b) {
  if(a < b) {
    a = b;
    return true;
  }
  return false;
}

template<class T>
inline bool chmin(T &a, T b) {
  if(a > b) {
    a = b;
    return true;
  }
  return false;
}

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


}