AC代码
#include <cstdio>
#include <iostream>
using namespace std;
int main()
{
int n;
while(scanf("%d",&n)!=EOF)
{
if(n==-1)
break;
int sum=0;
int speed[20]={0},time[20]={0};
cin>>speed[0]>>time[0];
sum=speed[0]*time[0];
for(int i=1;i<n;i++)
{
cin>>speed[i]>>time[i];
sum=sum+speed[i]*(time[i]-time[i-1]);
}
cout<<sum<<" miles"<<endl;
}
return 0;
}