#include <bits/stdc++.h>

using namespace std;

#define int long long

signed main() {
    ios_base::sync_with_stdio(false); cin.tie(0);

    int n;
    cin >> n;
    vector<int> c(n), h(n);
    for (int i = 0; i < n; i++) {
        cin >> c[i] >> h[i];
    }

    vector<int> maxc(n);
    maxc[n - 1] = c[n - 1];
    for (int i = n - 2; i >= 0; i--) {
        maxc[i] = max(maxc[i + 1], c[i]);
    }

    int ans = 0;
    int sum = 0;
    for (int i = 0; i < n; i++) {
        sum += h[i];
        if (c[i] == maxc[i]) {
            ans += sum * c[i];
            sum = 0;
        }
    }

    cout << ans << endl;
}