import sys
from math import sqrt, pi, sin
inp = lambda : sys.stdin.readline()[:-1]
mii = lambda x = " ": [*map(int,inp().split(x))]
mfi = lambda x = " ": [*map(float,inp().split(x))]
ii = lambda : int(inp())
p = ii()
n = ii()
r = ii()
crt = n
prev = n
ans = 0
while crt <= p:
crt += prev * r
prev *= r
ans += 1
print(ans)