poj 2017 Speed Limit

#include <iostream>#include <stdio.h>#include <algorithm>#include <string.h>#include <queue>#include <stack>#include <iomanip>#include <cmath>using namespace std;int n;int s[12],t[12];int main(){    while(cin>>n&&n!=-1)    {        t[0]=0;        for(int i=1;i<=n;i++) cin>>s[i]>>t[i];        int total=0;        for(int i=1;i<=n;i++) total+=(t[i]-t[i-1])*s[i];        cout<<total<<" miles"<<endl;    }    return 0;}