Stampede timer 1초 memory 256MB

Problem 1: Stampede [Brian Dean]

Farmer John's N cows (1 <= N <= 50,000) appear to be stampeding along the road at the front of FJ's farm, but they are actually just running in a foot race to see which cow is the fastest.

Viewed from above, each cow is represented by a unit-length horizontal line segment, specified by the coordinates of its left corner point at time t=0. For example, (-3,6) would specify a cow who at time t=0 is represented by the segment from (-3,6) to (-2,6). Each cow is moving to the right (in the +x direction) at a certain rate, specified by the integer amount of time it takes her to move 1 unit to the right.

FJ is not particularly thrilled that his cows are outside running instead of in the barn producing milk. He plans to admonish them with a stern lecture after the race ends. In order to determine which of his cows are participating in the race, FJ situates himself at (0,0) and looks along a ray extending in the +y direction. As the race unfolds, FJ sees a cow if she is ever the first cow visible along this ray. That is, a cow might not be visible if another cow is "in front" of her during the entire time she crosses FJ's line of sight.

Please compute the number of cows FJ can see during the entire race.

SOLUTION NOTES: FJ can see cows 1 and 2 but not cow 3.