func main()
	var s: []char :: cui@input()
	do s :: s.sub(0, s.findStr("pain", -1) + 1)
	
	var ans: int :: (^s - ^(s.replace("pon", ""))) / 3 - 1
	if(ans = 0)
		do ans :: -1
	end if
	do cui@print("\{ans}\n")
end func