t,s,q=map(int,input().split())
p=0
while s<t:s=s*q;p+=1
print(p)1154A - Restoring Three Numbers | 750A - New Year and Hurry |
705A - Hulk | 492B - Vanya and Lanterns |
1374C - Move Brackets | 1476A - K-divisible Sum |
1333A - Little Artem | 432D - Prefixes and Suffixes |
486A - Calculating Function | 1373B - 01 Game |
1187A - Stickers and Toys | 313B - Ilya and Queries |
579A - Raising Bacteria | 723A - The New Year Meeting Friends |
302A - Eugeny and Array | 1638B - Odd Swap Sort |
1370C - Number Game | 1206B - Make Product Equal One |
131A - cAPS lOCK | 1635A - Min Or Sum |
474A - Keyboard | 1343A - Candies |
1343C - Alternating Subsequence | 1325A - EhAb AnD gCd |
746A - Compote | 318A - Even Odds |
550B - Preparing Olympiad | 939B - Hamster Farm |
732A - Buy a Shovel | 1220C - Substring Game in the Lesson |