s = input()
n = len(s)
ans = 0
q = True
for i in range(n - 3):
    if q and s[i:i + 3] == "pon":
        ans += 1
    elif q and s[i:i + 4] == "pain":
        q = False
if q:
    print(-1)
else:
    if ans < 2:
        print(-1)
    else:
        print(ans - 1)