S = input()
ans = 0
p = ""
for s in S:
    if p == "pon":
        ans += 1
        p = ""
    elif p == "pain":
        break
    if s == "p" and p != "":
        p = ""
    p += s
else:
    if p != "pain":
        print(-1)
        exit()
if ans == 2:
    print(1)
elif ans <= 2:
    print(-1)
else:
    print(ans-1)