#include <bits/stdc++.h> using namespace std; int main(){ long int prize[1001],cabbage[1001],sumPrize=0; long int days,minPrize,dayPrize=0; cin>>days; for(int i=1;i<=days;i++) cin>>cabbage[i]>>prize[i]; minPrize=prize[1]; for(int j=1;j<=days;j++){ minPrize=min(minPrize,prize[j]); dayPrize=minPrize*cabbage[j]; sumPrize+=dayPrize; } cout<<sumPrize; }