673 B | 673 chars
import sys
from math import sqrt, pi, sin, factorial, ceil, floor
from datetime import datetime, timedelta
BLANK = " "
#inp = input
inp = lambda : sys.stdin.readline()[:-1].strip()
mii = lambda x = BLANK : [*map(int,inp().split(x))]
mfi = lambda x = BLANK : [*map(float,inp().split(x))]
ii = lambda : int(inp())
fi = lambda : float(inp())
p = print
def solve():
n, a, b = mii()
k = 1
for _ in range(b):
k *= a
k %= 26
s = input()
ans = ""
for i in s:
if i == ' ':
ans += i
else:
ans += chr((ord(i) - 65 - k + 26) % 26 + 65)
p(ans)
if __name__ == "__main__":
tc = 1
for t in range(1, tc+1):
ret = solve()