#include "bits/stdc++.h"
#define int long long
#define all(v) v.begin() , v.end()
#define sz(a) (int)a.size()
using namespace std;
void _(){
int n; cin >> n;
array<int,2> ar[n+5];
int pre[n+5],ans=0;
pre[0]=0;
for(int i=1;i<=n;i++){
cin >> ar[i][0] >> ar[i][1];
pre[i] = pre[i-1] + (ar[i][0] - ar[i][1]);
}
priority_queue<int> pq;
for(int i=1;i<n;i++){
if(pre[i] < 0){
ans -= pre[i];
pre[i] = 0;
}
ans += pre[i];
pq.push(pre[i]);
pq.push(pre[i]);
pq.pop();
}
while(!pq.empty()){
ans -= min(pre[n], pq.top());
pq.pop();
}
cout << ans << '\n';
}
int32_t main(){
cin.tie(0); ios::sync_with_stdio(0);
int tc=1;//cin >> tc;
while(tc--) _();
return 0;
}
