#include<bits/stdc++.h> using namespace std; int main(){ //大力水手吃蔬菜 int n,a,b,m; cin>>n; cin>>a>>b; int i=b; m=a*b; for(int i=2;i<=n;i++){ cin>>a>>b; if(b<i){ i=b; } m+=i*a; } cout<<m; return 0; }