#!/usr/bin/env python3
K, P, D = map(int, input().split())

novych_slepic = [0 for i in range(D+K+P+1)]
novych_vajec = [0 for i in range(D+K+P+1)]
slepic = 0

# Vylíhnutí naší první slepice
novych_slepic[K] = 1

for i in range(1, D+1):
    slepic += novych_slepic[i]
    novych_slepic[i+K] = novych_vajec[i]
    novych_vajec[i+P] = novych_vajec[i] + novych_slepic[i]

print(slepic)