#include<iostream> #include<cstring> #include<cstdio> using namespace std; int main(){ int n=0,i=0,a,b,num=0,min=101; cin>>n; for(i=0;i<n;i++){ cin>>a>>b; if(min> b) min = b; num += a*min; } cout << num <<endl; return 0; }