#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; }