A,B,T = map(int,raw_input().split())
ans = 0
array = []
stack = []
stack.append(ans)
while len(stack) != 0:
	ans = stack.pop()
	if ans >= T:
		array.append(ans)
		continue
	else:
		stack.append(ans+A)
		stack.append(ans+B)
print min(array)