#include <bits/stdc++.h>
using namespace std;
#define REP(i,a,n) for(int i=(a); i<(int)(n); i++)
#define rep(i,n) REP(i,0,n)
#define FOR(it,c) for(__typeof((c).begin()) it=(c).begin(); it!=(c).end(); ++it)
#define ALLOF(c) (c).begin(), (c).end()
typedef long long ll;
typedef unsigned long long ull;


int main(){
  int N;
  cin >> N;
  vector<ll> v;
  rep(i,N){
    ll a, b;
    cin >> a >> b;
    v.push_back(a-b);
  }

  vector<ll> sum(N+1);
  ll base = 0;
  rep(i,N){
    base += v[i];
    sum[i] = base;
  }

  ll ret = -base;
  rep(i,N){
    ret = max(ret, sum[i] - (base-sum[i]));
  }

  cout << ret << endl;
  
  return 0;
}