import java.io.*;
import java.util.*;

class Process {
    private String[][] A;

    Process(String[][] A) {
        this.A = A;
    }

    int getResult() {
        var nyanpassCounts = new int[A.length];
        for(int i = 0; i < A.length; i++) {
            for(int j = 0; j < A[0].length; j++) {
                if(A[i][j].equals("nyanpass")) {
                    nyanpassCounts[j]++;
                }
            }
        }
        
        var renchonLikeVillagerNums = new ArrayList<Integer>();
        for(int i = 0; i < nyanpassCounts.length; i++) {
            if(nyanpassCounts[i] == (A.length - 1)) {
                renchonLikeVillagerNums.add((i + 1));
            }
        }

        return ((renchonLikeVillagerNums.size() == 1) ? renchonLikeVillagerNums.get(0) : -1);
    }
}

public class Main {
    public static void main(String[] args) throws IOException {
        var bufferedReader = new BufferedReader(new InputStreamReader(System.in));
        var printWriter    = new PrintWriter(new BufferedWriter(new OutputStreamWriter(System.out)));

        // 入力
        int N = Integer.parseInt(bufferedReader.readLine().trim());

        var A = new String[N][N];
        for(int i = 0; i < N; i++) {
            A[i] = bufferedReader.readLine().trim().split("[ ]+");
        }

        // 処理および出力
        printWriter.println((new Process(A)).getResult());
        
        bufferedReader.close();
        printWriter.close();
    }
}