import std.conv, std.functional, std.range, std.stdio, std.string;
import std.algorithm, std.array, std.bigint, std.bitmanip, std.complex, std.container, std.math, std.mathspecial, std.numeric, std.regex, std.typecons;
import core.bitop;

class EOFException : Throwable { this() { super("EOF"); } }
string[] tokens;
string readToken() { for (; tokens.empty; ) { if (stdin.eof) { throw new EOFException; } tokens = readln.split; } auto token = tokens.front; tokens.popFront; return token; }
int readInt() { return readToken.to!int; }
long readLong() { return readToken.to!long; }
real readReal() { return readToken.to!real; }

bool chmin(T)(ref T t, in T f) { if (t > f) { t = f; return true; } else { return false; } }
bool chmax(T)(ref T t, in T f) { if (t < f) { t = f; return true; } else { return false; } }

int binarySearch(alias pred, T)(in T[] as) { int lo = -1, hi = cast(int)(as.length); for (; lo + 1 < hi; ) { const mid = (lo + hi) >> 1; (unaryFun!pred(as[mid]) ? hi : lo) = mid; } return hi; }
int lowerBound(T)(in T[] as, T val) { return as.binarySearch!(a => (a >= val)); }
int upperBound(T)(in T[] as, T val) { return as.binarySearch!(a => (a > val)); }




void main() {
  try {
    for (; ; ) {
      const N = readInt();
      auto A = new string[N];
      foreach (i; 0 .. N) {
        A[i] = readToken();
      }
      const M = readInt();
      auto B = new string[M];
      foreach (i; 0 .. M) {
        B[i] = readToken();
      }
      
      char[] csA, csB;
      foreach (i; 0 .. N) {
        foreach (c; A[i]) {
          csA ~= c;
        }
      }
      foreach (i; 0 .. M) {
        foreach (c; B[i]) {
          csB ~= c;
        }
      }
      csA = cast(char[])((cast(byte[])(csA)).sort.array);
      csB = cast(char[])((cast(byte[])(csB)).sort.array);
      assert(csA == csB);
      const V = cast(int)(csA.length);
      auto adj = new bool[][](V, V);
      foreach (i; 0 .. N) {
        foreach (j; 0 .. cast(int)(A[i].length) - 1) {
          const u = csA.lowerBound(A[i][j]);
          const v = csA.lowerBound(A[i][j + 1]);
          adj[u][v] = true;
        }
      }
      foreach (i; 0 .. M) {
        foreach (j; 0 .. cast(int)(B[i].length) - 1) {
          const u = csA.lowerBound(B[i][j]);
          const v = csA.lowerBound(B[i][j + 1]);
          adj[u][v] = true;
        }
      }
      int numEdges;
      foreach (u; 0 .. V) foreach (v; 0 .. V) {
        if (adj[u][v]) {
          ++numEdges;
        }
      }
      if (numEdges == V - 1) {
        string ans;
        foreach (u; 0 .. V) {
          if (iota(V).all!(v => !adj[v][u])) {
            for (int v = u; ; ) {
              ans ~= csA[v];
              foreach (w; 0 .. V) {
                if (adj[v][w]) {
                  v = w;
                  goto found;
                }
              }
              break;
             found:
            }
            break;
          }
        }
        writeln(ans);
      } else {
        writeln(-1);
      }
    }
  } catch (EOFException e) {
  }
}