#include <iostream> using namespace std; int main() { int n,a[100001],sum = 0,s = 100000; cin >> n; for(int i = 1;i <= n*2;i++) { cin >> a[i]; } for(int i = 2;i <= n*2;i+=2) { if(s > a[i]) { s = a[i]; } } for(int i = 1;i <= n*2;i+=2) { sum+=s*a[i]; } cout << sum; return 0; }