import sys
from collections import deque, Counter
input = lambda: sys.stdin.readline().rstrip()
ii = lambda: int(input())
mi = lambda: map(int, input().split())
li = lambda: list(mi())
inf = 2 ** 63 - 1
mod = 998244353
import sys
input = lambda: sys.stdin.readline().rstrip()
ii = lambda: int(input())
mi = lambda: map(int, input().split())
li = lambda: list(mi())
mod = 998244353
def floor_sum(n,m,a,b):
    ans=0
    if a>=m:
        ans+=(n-1)*n*(a//m)//2
        a%=m
    if b>=m:
        ans+=n*(b//m)
        b%=m
    y_max=(a*n+b)//m
    x_max=(y_max*m-b)
    if y_max==0:
        return ans
    ans+=(n-(x_max+a-1)//a)*y_max
    ans+=floor_sum(y_max,a,m,(a-x_max%a)%a)
    return ans

def mod_le(n, a, b, k, m):
    #0 <= x < n について、 (a * x + b) mod m < k なるものの個数を求める
    return floor_sum(n, m, a, b + m) - floor_sum(n, m, a, b - k + m)


for _ in range(1):
    l, r, c = mi()
    n = r - l + 1
    m = 1000
    a = (- c) % m
    b = (1000 - l * c) % m
    if a == 0:
        print(b % m)
        continue
    ok = m
    ng = 0
    while abs(ok - ng) > 1:
        mid = (ok + ng) // 2
        if mod_le(n, a, b, mid, m):
            ok = mid
        else:
            ng = mid
    print(ok - 1)