#include<iostream>
#include<cstdio>
#include<algorithm>
#include<cmath>
using namespace std;
int w[100005],score[100005];
int main()
{
int n;
int y,result;
while(cin>>n)
{result=0;
for(int i=0;i<n;i++)
{
cin>>w[i]>>score[i];
result+=w[i]*score[i];
}
if(result<0)cout<<0;
else
cout<<result;
cout<<endl;
}
return 0;
}