#include <iostream>
#include <stdio.h>
#include <string.h>
using namespace std;

int letters[301];
int let[301];
char word[101];
int n;
int L;

int main()
{
    freopen("anagrams.in","r",stdin);
    freopen("anagrams.out","w",stdout);

    int i,j;

    memset(letters,0,sizeof(letters));

    scanf("%d",&n);

    scanf("%s",word+1);
    L=strlen(word+1);

    for (i=1;i<=L;i++)
    {
        letters[ (int)word[i] ]++;
    }

    for (i=2;i<=n;i++)
    {
        scanf("%s",word+1);
        L=strlen(word+1);

        memset(let,0,sizeof(let));

        for (j=1;j<=L;j++)
        {
            let[ (int)word[j] ]++;
        }

        for (j=1;j<=300;j++)
        {
            if (let[j]!=letters[j])
            {
                printf("-1\n");
                return 0;
            }
        }
    }

    for (i=1;i<=300;i++)
    {
        for (j=1;j<=letters[i];j++)
        {
            cout<<(char)i;
        }
    }
    cout<<endl;

    return 0;
}