#include <bits/stdc++.h>
using namespace std;
using ll = long long;
int main() {
ios::sync_with_stdio(0);
cin.tie(0);
int n;
cin >> n;
vector<int> a(n), b(n);
stack<pair<int, int>> left, right;
ll res = 0;
for (int i = 0; i < n; ++i) {
cin >> a[i] >> b[i];
int need = min(a[i], b[i]);
a[i] -= need;
b[i] -= need;
}
for (int i = n - 1; i >= 0; --i) {
if (a[i] > 0) {
right.push({a[i], i});
}
}
for (int i = 0; i < n; ++i) {
while (right.size() && right.top().second <= i) {
left.push({right.top()});
right.pop();
}
while (b[i] > 0) {
if (left.size()) {
int need = min(b[i], left.top().first);
b[i] -= need;
left.top().first -= need;
int d = abs(i - left.top().second);
res += 1LL * d * need;
} else {
int need = min(b[i], right.top().first);
b[i] -= need;
right.top().first -= need;
int d = abs(i - right.top().second);
res += 1LL * d * need;
}
while (left.size() && left.top().first == 0) left.pop();
while (right.size() && right.top().first == 0) right.pop();
}
}
// cout << "CNT: " << cnt << endl;
cout << res << endl;
}
