#include<bits/stdc++.h> using namespace std; int a[1002],b[1002]; int main() { int n; cin>>n; int x=0; for(int l=1;l<=n;l++) { cin>>a[l]>>b[l]; } int min0=b[1]; int i=1; while(i<=n) { min0=min(min0,b[i]); x+=min0*a[i]; i++; } cout<<x; return 0; }