let s = stdin.ReadLine ()

let mutable pon_count = 0
let mutable prev = 'n'
for i in 0..s.Length-1 do
    if s.[i..i+3] = "pain" then
        printfn "%d" (if pon_count < 2 then -1 else pon_count - 1)
        exit 0
    else
        match prev, s.[i] with
        | 'n', 'p' ->
            prev <- 'p'
        | 'p', 'o' ->
            prev <- 'o'
        | 'o', 'n' ->
            prev <- 'n'
            pon_count <- pon_count + 1
        | _ ->
            ()
            
printfn "-1"