Author:  A. Baranov  Time limit:  1 sec  
Input file:  Standard input  Memory limit:  256 Mb  
Output file:  Standard output 
"Ferryman of Hades" is a simple arcade game based on the Greek mythology. The main scene of the game is Styx river that is represented as a 1dimensional line. Souls fall down from height H to this line. Charon must catch them in his boat when they touch the river line.
The boat of Charon is represented as a closed segment (containing its boundary points) of length L moving along line from the initial position [0, L].
Boat can move only from left to right with a fixed integer speed. It is known that ith soul falls down to point P_{i} with a speed V_{i}.
A soul is caught if by the moment it crosses the river line, this point belongs to the boat.
Your program must, given H, L, P_{i}, and V_{i}, determine the minimum possible integer speed of the boat maximizing the number of caught souls.
Input contains integers H, L, and n, followed by n pairs of integers P_{i}, V_{i}.
Output must contain a single integer — the speed of the boat.
0 < (H, L, V_{i}) ≤ 10^{6}, 0 ≤ P_{i} ≤ 10^{6},
1 ≤ n ≤ 2 ⋅ 10^{5}
No.  Standard input  Standard output 

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