X = int(input())
Y = int(input())
L = int(input())

import math

def process_counter(X,Y,L):
    counter=0
    if Y<0:
        counter+=2
    else:
        counter+=1
    counter+=math.ceil(Y/L)
    counter+=math.ceil(X/L)
    return counter
    
print(process_counter(X,Y,L))