import java.io.IOException;
import java.util.InputMismatchException;

public class Main {
	int compare(StringBuilder a, StringBuilder b) {
		//		if (a.charAt(0) == b.charAt(0) && a.length() == 1) {
		//			return 1;
		//		}
		//		if (a.charAt(0) == b.charAt(0) && b.length() == 1) {
		//			return -1;
		//		}
		int length = Math.min(a.length(), b.length());
		for (int i = 0; i < length; i++) {
			if (a.charAt(i) != b.charAt(i)) {
				return a.charAt(i) - b.charAt(i);
			}
		}
		return 0;
	}

	void run() {
		MyScanner sc = new MyScanner();

		int n = sc.nextInt();
		StringBuilder[] c = new StringBuilder[n];
		int cnt = 0;
		for (int i = 0; i < n; i++) {
			c[i] = new StringBuilder(sc.next() + '{');
			cnt += c[i].length()-1;
		}

		StringBuilder s = new StringBuilder("");
		while (true) {
			int min = -1;
			for (int i = 0; i < n; i++) {
				if (0 < c[i].length()) {
					if (min == -1 || compare(c[i], c[min]) < 0) {
						min = i;
					}
				}
			}
			s = s.append(c[min].charAt(0));
			c[min].deleteCharAt(0);
			if (s.length() == cnt) {
				break;
			}
		}
		System.out.println(s.toString());
	}

	public static void main(String[] args) {
		new Main().run();
	}

	public void mapDebug(int[][] a) {
		System.out.println("--------map display---------");
		for (int i = 0; i < a.length; i++) {
			for (int j = 0; j < a[i].length; j++) {
				System.out.printf("%3d ", a[i][j]);
			}
			System.out.println();
		}
		System.out.println("----------------------------" + '\n');
	}

	class MyScanner {
		int read() {
			try {
				return System.in.read();
			} catch (IOException e) {
				throw new InputMismatchException();
			}
		}

		boolean isSpaceChar(int c) {
			return c == ' ' || c == '\n' || c == '\r' || c == '\t' || c == -1;
		}

		boolean isEndline(int c) {
			return c == '\n' || c == '\r' || c == -1;
		}

		int nextInt() {
			return Integer.parseInt(next());
		}

		int[] nextIntArray(int n) {
			int[] array = new int[n];
			for (int i = 0; i < n; i++)
				array[i] = nextInt();
			return array;
		}

		long nextLong() {
			return Long.parseLong(next());
		}

		long[] nextLongArray(int n) {
			long[] array = new long[n];
			for (int i = 0; i < n; i++)
				array[i] = nextLong();
			return array;
		}

		double nextDouble() {
			return Double.parseDouble(next());
		}

		double[] nextDoubleArray(int n) {
			double[] array = new double[n];
			for (int i = 0; i < n; i++)
				array[i] = nextDouble();
			return array;
		}

		String next() {
			int c = read();
			while (isSpaceChar(c))
				c = read();
			StringBuilder res = new StringBuilder();
			do {
				res.appendCodePoint(c);
				c = read();
			} while (!isSpaceChar(c));
			return res.toString();
		}

		String[] nextStringArray(int n) {
			String[] array = new String[n];
			for (int i = 0; i < n; i++)
				array[i] = next();

			return array;
		}

		String nextLine() {
			int c = read();
			while (isEndline(c))
				c = read();
			StringBuilder res = new StringBuilder();
			do {
				res.appendCodePoint(c);
				c = read();
			} while (!isEndline(c));
			return res.toString();
		}
	}
}