#include <bits/stdc++.h>   int a[100005] = {};   int p[100005] = {};   int mbuy[100005] = {};   int main() {     std::ios_base::sync_with_stdio(false);     std::cin.tie(NULL);     std::cout.tie(NULL);     int n, currmin = 1000000, buy = 0, last = 0;     std::cin >> n;     for (int i = 0; i < n; i++) std::cin >> a[i] >> p[i];     for (int i = 0; i < n; i++) {       if (p[i] < currmin) {         mbuy[last] = buy;         currmin = p[i];         last = i;         buy = 0;       }       buy += a[i];     }     mbuy[last] = buy;     long long int ans = 0;     for (int i = 0; i < n; i++) {       ans += mbuy[i] * p[i];     }     std::cout << ans <<   n ;   }   