#include <bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>
#define ll long long
#define endl "\n"
using namespace std;
using namespace __gnu_pbds;
mt19937_64 rng(chrono::steady_clock::now().time_since_epoch().count());
template <typename T, typename key = less<T>>
using ordered_set = tree<T, null_type, key, rb_tree_tag, tree_order_statistics_node_update>;
void solve()
{
ll n;
cin >> n;
ll a[n];
{
ll sum = 0;
for (ll i = 0; i < n; i++)
{
ll x, y;
cin >> x >> y;
sum += x - y;
a[i] = sum;
}
}
ll ans = 0;
priority_queue<ll> q;
for (ll i = 0; i < n - 1; i++)
{
if (a[i] < 0) ans -= a[i], a[i] = 0;
ans += a[i];
q.push(a[i]);
q.push(a[i]);
q.pop();
}
while (!q.empty())
{
ans -= min(q.top(), a[n - 1]);
q.pop();
}
cout << ans << endl;
}
int main()
{
ios_base::sync_with_stdio(0);
cin.tie(0);
ll t = 1;
// precomp();
// cin >> t;
for (ll cs = 1; cs <= t; cs++)
solve();
// cerr << "\nTime elapsed: " << clock() * 1000.0 / CLOCKS_PER_SEC << " ms\n";
}
