#include<iostream> #include<cstring> using namespace std; int main(){ int n,a,b,s=0,x; cin>>n; cin>>a>>b; x=b; s+=a*b; for(int i=1;i<n;i++){ cin>>a>>b; if(x<b) b=x; else if(x>b) x=b; s+=a*b; }cout<<s; return 0; }