Simple pattern matching

This program has been disqualified.

Source code:

import random

if not input:
	opp_history = ''
	output = random.choice('RPS')
else:
	opp_history += input
	throw = ''
	for length in range(min(len(opp_history)/2-1,10),0,-1):
		last_throws = opp_history[-length:]
		occurences = []
		for i in range(len(opp_history)-length):
			if opp_history[i:i+length] == last_throws:
				occurences.append(i)
		if occurences:
			prob_throws = [opp_history[place+1] for place in occurences]
			r, p, s = prob_throws.count('R'), prob_throws.count('P'), prob_throws.count('S')
			if r > max(p, s): throw = 'P'
			elif p > max(r, s): throw = 'S'
			elif s > max(r, p): throw = 'R'
			elif r==p==s: throw = random.choice('RPS')
			elif r == s: throw = random.choice('PS')
			elif  p==s: throw = random.choice('SR')
			else: throw = random.choice('RP')
			break
	output = throw if throw else random.choice('RPS')