#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
int N;
ll ans = 0; // value of DP function at 0
priority_queue<ll> points; // points where DP function changes slope
int main() {
cin >> N;
vector<ll> dif(N + 1);
for (int i = 1; i <= N; ++i) {
int a, b;
cin >> a >> b;
dif[i] = a - b + dif[i - 1];
}
assert(dif[N] >= 0); // assume solution exists
for (int i = 1; i < N; ++i) {
if (dif[i] < 0) ans -= dif[i], dif[i] = 0;
if (dif[i] > dif[N]) ans += (dif[i] - dif[N]), dif[i] = dif[N];
ans += dif[i];
points.push(dif[i]);
points.push(dif[i]);
points.pop();
}
while (points.size()) {
ll a = points.top();
points.pop();
ans -= a;
}
cout << ans << "\n";
}
