S = input()
n = len(S)

pon = "pon"
pon_ind = 0
pain = "pain"
pain_ind = 0
cnt = 0
for i in range(n):
    if S[i] == pon[pon_ind]:
        pon_ind += 1
        if pon_ind == 3:
            cnt += 1
            pon_ind = 0
    elif pon_ind > 0:
        pon_ind = 0
    if S[i] == pain[pain_ind]:
        pain_ind += 1
        if pain_ind == 4:
            if cnt < 2:
                print(-1)
            else:
                print(cnt - 1)
            exit()
    elif pain_ind > 0:
        pain_ind = 0
print(-1)