As we all know,a large wave of leadership were approaching these days.Now,-10 wants to calculate the time that N leadership's cars pass through gate should be takes.
And at the beginning, all the buses are close to each other without any space, and they have different lengths and the largest speeds.We assume any leadership's car can reach the speed that isn’t beyond the maximal speed at once.And the distance of two leaderships is fixed,of course,the distance will not change when they passes.
Now -10 wants you to calculate minimal time all the leaderships pass successively(依次).

There are many cases. For each case, there is two intergers N(1<=N<=100), representing the number of the leaderships. There are two interges in the following N lines, for the length of leadership' s car Li(meter, 1<=Li<=100) and the maximal speed Vi(meter/second, 1<=V<=100) of the i-th leadership's car.

For each case, print the result obtaining two digits after the decimal point.