#include<iostream> #include<cmath> #include<iomanip> #include<cstdio> using namespace std; int main() { int n,a,b,ndd = 101,s = 0; cin>>n; for(int i=1;i<=n;i++){ cin>>a>>b; if(ndd > b){ ndd = b; } s += a * ndd; } cout<<s; }