import java.io.InputStream;
import java.io.PrintStream;
import java.util.Arrays;
import java.util.Scanner;

public class Main {
	InputStream in = System.in;
	PrintStream out = System.out;

	public void _main(String[] args) {
		Scanner sc = new Scanner(in);

		String S = sc.next();

		sc.close();

		char[] c = new char[S.length()];
		S.getChars(0, S.length(), c, 0);

		Arrays.sort(c);

		if (c[0] == c[1] && c[2] == c[3] && c[0] != c[2]) {
			out.println("Yes");
		} else {
			out.println("No");
		}

	}

	public static void main(String[] args) {
		new Main()._main(args);
	}
} import java.io.InputStream; InputStream java.io import java.io.PrintStream; PrintStream java.io import java.util.Arrays; Arrays java.util import java.util.Scanner; Scanner java.util public class Main {
	InputStream in = System.in;
	PrintStream out = System.out;

	public void _main(String[] args) {
		Scanner sc = new Scanner(in);

		String S = sc.next();

		sc.close();

		char[] c = new char[S.length()];
		S.getChars(0, S.length(), c, 0);

		Arrays.sort(c);

		if (c[0] == c[1] && c[2] == c[3] && c[0] != c[2]) {
			out.println("Yes");
		} else {
			out.println("No");
		}

	}

	public static void main(String[] args) {
		new Main()._main(args);
	}
} Main InputStream in = System.in; in System.in System System.in PrintStream out = System.out; out System.out System System.out public void _main(String[] args) {
		Scanner sc = new Scanner(in);

		String S = sc.next();

		sc.close();

		char[] c = new char[S.length()];
		S.getChars(0, S.length(), c, 0);

		Arrays.sort(c);

		if (c[0] == c[1] && c[2] == c[3] && c[0] != c[2]) {
			out.println("Yes");
		} else {
			out.println("No");
		}

	} _main {
		Scanner sc = new Scanner(in);

		String S = sc.next();

		sc.close();

		char[] c = new char[S.length()];
		S.getChars(0, S.length(), c, 0);

		Arrays.sort(c);

		if (c[0] == c[1] && c[2] == c[3] && c[0] != c[2]) {
			out.println("Yes");
		} else {
			out.println("No");
		}

	} Scanner sc = new Scanner(in); sc new Scanner(in) String S = sc.next(); S sc.next() sc.next sc sc.close() sc.close sc char[] c = new char[S.length()]; c new char[S.length()] S.length() S.length S S.getChars(0, S.length(), c, 0) S.getChars S 0 S.length() S.length S c 0 Arrays.sort(c) Arrays.sort Arrays c if (c[0] == c[1] && c[2] == c[3] && c[0] != c[2]) {
			out.println("Yes");
		} else {
			out.println("No");
		} c[0] == c[1] && c[2] == c[3] && c[0] != c[2] c[0] == c[1] && c[2] == c[3] && c[0] != c[2] c[0] == c[1] c[0] c 0 c[1] c 1 c[2] == c[3] c[2] c 2 c[3] c 3 c[0] != c[2] c[0] c 0 c[2] c 2 {
			out.println("Yes");
		} out.println("Yes") out.println out "Yes" {
			out.println("No");
		} out.println("No") out.println out "No" String[] args args public static void main(String[] args) {
		new Main()._main(args);
	} main {
		new Main()._main(args);
	} new Main()._main(args) new Main()._main new Main() args String[] args args public class Main {
	InputStream in = System.in;
	PrintStream out = System.out;

	public void _main(String[] args) {
		Scanner sc = new Scanner(in);

		String S = sc.next();

		sc.close();

		char[] c = new char[S.length()];
		S.getChars(0, S.length(), c, 0);

		Arrays.sort(c);

		if (c[0] == c[1] && c[2] == c[3] && c[0] != c[2]) {
			out.println("Yes");
		} else {
			out.println("No");
		}

	}

	public static void main(String[] args) {
		new Main()._main(args);
	}
} public class Main {
	InputStream in = System.in;
	PrintStream out = System.out;

	public void _main(String[] args) {
		Scanner sc = new Scanner(in);

		String S = sc.next();

		sc.close();

		char[] c = new char[S.length()];
		S.getChars(0, S.length(), c, 0);

		Arrays.sort(c);

		if (c[0] == c[1] && c[2] == c[3] && c[0] != c[2]) {
			out.println("Yes");
		} else {
			out.println("No");
		}

	}

	public static void main(String[] args) {
		new Main()._main(args);
	}
} Main
import java.io.InputStream;
import java.io.PrintStream;
import java.util.Arrays;
import java.util.Scanner;

public class Main {
	InputStream in = System.in;
	PrintStream out = System.out;

	public void _main(String[] args) {
		Scanner sc = new Scanner(in);

		String S = sc.next();

		sc.close();

		char[] c = new char[S.length()];
		S.getChars(0, S.length(), c, 0);

		Arrays.sort(c);

		if (c[0] == c[1] && c[2] == c[3] && c[0] != c[2]) {
			out.println("Yes");
		} else {
			out.println("No");
		}

	}

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