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

remainder_list = []
remainder_count = 0
if L == R:
    remainder_count = 1
else:
    for i in range(L, R + 1):
        rem = i % M
        if rem not in remainder_list:
            remainder_list.append(rem)

remainder_count += len(remainder_list)

print(remainder_count)