#include <bits/stdc++.h>
#define rep(i,n) for(int i=0;i<n;i++)
using namespace std;
typedef long long ll;
typedef pair<ll,int> P;
const ll INF = 1e12;
const int MOD = 1000000007;


int main() {
        int n;
        cin >> n;
        vector<ll> a(n+1);
        rep(i,n){
                ll p,q;
                cin >> p >> q;
                a[i+1] = p - q;
        }
        ll ans = 0;
        rep(i,n) a[i+1] += a[i];
        rep(i,n+1){
                ll now = a[i] - (a[n] - a[i]);
                ans = max(ans,now);
        }

        cout << ans << endl;
   

        return 0;
}