#include <bits/stdc++.h>

using namespace std;

#define REP(i,n) for(int i=0; i<(int)(n); i++)
#define FOR(i,b,e) for (int i=(int)(b); i<(int)(e); i++)
#define ALL(x) (x).begin(), (x).end()

const double PI = acos(-1);

int main() {
  ios_base::sync_with_stdio(0);
  cin.tie(0);

  int n;
  cin >> n;
  vector<long long> sum(n+1);
  REP (i, n) {
    int l, r;
    cin >> l >> r;
    sum[i+1] = sum[i] + l - r;
  }

  long long ret = 0;
  for (int i = 1; i <= n; i++) {
    ret = max(ret, sum[i-1] + abs(sum[i] - sum[i-1]) - sum[n] + sum[i]);
  }
  cout << ret << endl;
  
  return 0;
}