#include <bits/stdc++.h>
#define rep(i,n) for(int i = 0; i < (n); i++)
using namespace std;
typedef long long ll;

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

    int N; cin >> N;
    vector<ll> D;
    rep(i,N){
        ll a,b; cin >> a >> b;
        D.emplace_back(a - b);
    }

    vector<ll> S(N+1,0);
    rep(i,N) S[i+1] = S[i] + D[i];

    ll ans = -1e18;
    rep(i,N+1) ans = max(ans, S[i] - (S[N] - S[i]));
    cout << ans << endl;
}