#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
typedef pair<int, int> P;
#define rep(i, n) for (int i = 0; i < (int)(n); ++i)
#define all(x) (x).begin(),(x).end()
template <class T> inline bool chmin(T &a, T b) {if (a > b){a = b;return true;}return false;}
template <class T> inline bool chmax(T &a, T b) {if (a < b){a = b;return true;}return false;}

int main(){
    cin.tie(0);
    ios::sync_with_stdio(false);
    ll n;cin>>n;
    vector<pair<ll,ll>> a(n);
    ll sum=0;
    rep(i, n){
        ll p,q;cin>>p>>q;
        a[i] = make_pair(p,q);
        sum+=(p-q);
    }
    ll ans = sum;
    for(int i=n-1;i>=0;i--){
        pair<ll,ll> p = a[i];
        sum = sum-(p.first-p.second)+(p.second-p.first);
        ans = max(ans, sum);
    }
    cout<<ans<<endl;
}