CCC 2020 J2: Epidemiology

This is a math question.

if R > 1, then days = log(1 + (P*(R-1)+1)/N, R)

else, days = P/N

import math

P = int(input())
N = int(input())
R = int(input())
if R > 1:
    M1 = 1 + (P*(R-1)+1)/N
    days = int(math.log(M1,R))
else:
    days = P//N
print(days)