num_list = list(map(int, input().split()))
L, R, M = num_list[0], num_list[1], num_list[2]

remainders = set()
remainder_count = 0
if L == R:
    remainder_count = 1
else:
    for i in range(L, R + 1):
        remainders.add(i % M)
remainder_count += len(remainders)

print(remainder_count)