package Yukicoder

/**
 * Created by hichikawa on 2015/11/12.
 */
fun main(args: Array<String>) {
    fun readLineStringArray() : List<String> {
        val str = readLine() as String
        val arrStr = str.split(" ")
        return arrStr
    }
    fun readLineInt() : Int {
        val str = readLine() as String
        return str.toInt()
    }

    val num = readLineInt()
    var arrFlag = Array<Boolean>(num, {true})
    for (i in 1..num) {
        val strArray = readLineStringArray()
        for ((i, stri) in strArray.withIndex()) {
            when (stri) {
                "nyanpass" -> 0
                "-" -> 0
                else -> arrFlag[i] = false
            }
        }
    }
    var retNum = -1
    for ((i, boo) in arrFlag.withIndex()) {
        if (boo) {
            if (retNum == -1) {
                retNum = i+1
            } else {
                println(-1)
                return
            }
        }
    }
    println(retNum)
}