Easter Party

package main

import "fmt"

func main() {
    var guests int
    fmt.Scanln(&guests)

    var envelope, budget float64
    fmt.Scanln(&envelope)
    fmt.Scanln(&budget)

    sum := float64(guests) * envelope

    if guests >= 10 && guests <= 15 {
        sum *= 0.85
    } else if guests > 15 && guests <= 20 {
        sum *= 0.80
    } else if guests > 20 {
        sum *= 0.75
    }

    sum += budget / 10

    if budget >= sum {
        fmt.Printf("It is party time! %.2f leva left.\n", budget - sum)
    } else {
        fmt.Printf("No party! %.2f leva needed.\n", sum - budget)
    }
}