let s = stdin.ReadLine ()

let mutable pon_count = 0
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
    elif s.[i..i+2] = "pon" then
        pon_count <- pon_count + 1
            
printfn "-1"