#include<iostream>
#include <vector>
using namespace std;
using ll = long long ;
const ll longinf = 1LL << 60;

int main() {
    int n;
    cin>>n;
    vector<ll> a(n+1);
    for(int i=0;i<n;i++){
        int x,y;
        cin>>x>>y;
        a[i+1]=x-y;
    }
    for(int i=0;i<n;i++)a[i+1]+=a[i];
    ll ans = 0;
    for(int i=0;i<=n;i++){
        ans = max(ans,2*a[i]-a[n]);
    }
    cout<<ans<<endl;
    return 0;
}