#include<iostream>
 using namespace std;
 int b[1000];
  int main(){
    int m,sum,a;
    while(cin>>m){
      if(m==-1)break;
      sum=0;
      for(int i=1;i<=m;i++){
      	cin>>a>>b[i];
        sum+=a*(b[i]-b[i-1]);
      }
      cout<<sum<<" miles"<<endl;
    }
  }