Our jeep is in the desert and must reach a point which is N kilometres away from it. The terrain is tough, the car is old, and it seems like the fuel flows out, and because of this on every kilometre travelled, one litre of fuel is spent. But the jeep has fuel-cans and fuel tank with total capacity of M < N litres. On other hand, at the beginning of the road there is unlimited amount of fuel, and everywhere in the desert there are empty cisterns, in which the jeep, passing near them, can leave unlimited amount of fuel.

Write a program which calculates the minimum amount of fuel in litres which is needed to reach the destination point.

Two integers N and M are written on the only line of input. It is known that 5M ≥ N > 0. (N < 32000).

The result (the minimum liters of fuel, eventually rounded up), must be written on the only line of output.