POJ 1922 Ride to School

#include <iostream>
#include <cmath>
using namespace std;

int speed;
int stime;
double dtime;

int main()
{
int n, min, i;
while (cin >> n)
{
if (n == 0)
break;
min = 1000000;
for (i = 0; i < n; i++)
{
cin >> speed >> stime;
if (stime >= 0)
{
dtime = ceil((double)4.5 / speed * 3600) + stime;
if (dtime < min)
min = dtime;
}
}
cout << min << endl;
}
}