1.1 KB | 1102 chars
"""
[6426: Psuedo-Random Numbers](https://www.acmicpc.net/problem/6426)
Tier: Bronze 1
Category: arithmetic, implementation, math, simulation
"""
import sys
from math import sqrt, pi, sin, factorial, ceil, floor
from datetime import datetime, timedelta
SYS_INPUT = True
RECURSION_LIMIT = 10 ** 7
SET_RECURSION = False
BLANK = " "
if SET_RECURSION:
sys.setrecursionlimit(RECURSION_LIMIT)
inp = lambda : sys.stdin.readline().rstrip() if SYS_INPUT else input()
mii = lambda : [*map(int,inp().split())]
mfi = lambda : [*map(float,inp().split())]
ii = lambda : int(inp())
fi = lambda : float(inp())
isplit = lambda : inp().split()
p = print
def gcd(a, b): return gcd(b, a % b) if b > 0 else a
def lcm(a, b): return a * b // gcd(a, b)
def solve():
tc = 1
while 1:
Z, I, M, L = mii()
if Z == I == M == L == 0:
break
d = {}
cnt = 0
while d.get(L, None) == None:
d[L] = cnt
L = (Z * L + I) % M
cnt += 1
p("Case {}: {}".format(tc, cnt - d[L]))
tc += 1
if __name__ == "__main__":
tc = 1
for t in range(1, tc+1):
ret = solve()