Hackerrank Sherlock and The Beast implementation in Scala

Sherlock and The Beast.scala

import scala.math.BigInt
object Solution {
  def main(args: Array[String]) {
    val lines = io.Source.stdin.getLines().drop(1).toList
    val nums = lines.map(l => l.toInt)
    def decentNum(n: Int) : String ={        
        for( i <- (n to 0 by -1) ) {
            if( i % 3 ==0 && (n -i) % 5 ==0 ) return ("5" * i  + "3" * (n-i))
        }
        return "-1";
    }
    nums.foreach( n => println(decentNum(n)))
  }
}