Решение

import java.io.BufferedReader
import java.io.BufferedWriter
import java.io.InputStreamReader
import java.io.OutputStreamWriter

fun main() {
    val reader = BufferedReader(InputStreamReader(System.`in`))
    val writer = BufferedWriter(OutputStreamWriter(System.out))
    val a = reader.readLine().toInt()
    val b = reader.readLine().toInt()
    val c = reader.readLine().toInt()

    if (c < 0) {
        writer.write("NO SOLUTION")
    } else if (a == 0) {
        if (b == c * c) {
            writer.write("MANY SOLUTIONS")
        } else {
            writer.write("NO SOLUTION")
        }
    } else {
        val numerator = c * c - b
        if (numerator % a == 0) {
            val x = numerator / a
            if (a.toLong() * x + b >= 0) {
                writer.write(x.toString())
            } else {
                writer.write("NO SOLUTION")
            }
        } else {
            writer.write("NO SOLUTION")
        }
    }

    writer.flush()
    reader.close()
    writer.close()
}