
import java.util.Scanner;
class Main {
    public static void main(String[] args) {
        Scanner input=new Scanner(System.in);
        char []S;
        int count=0;
        S=input.next().toCharArray();
        for(int i=0;i<3;i++)
        {
            for(int j=i+1;j<4;j++)
            {
                if(S[i]==S[j])
                {
                    count++;
                }
            }
        }
        if(count==2)
        {
            System.out.println("Yes");
        }
        else
            System.out.println("No");
    }
}

/tmp/hf-datasets-cache/medium/datasets/42704881117311-config-parquet-and-info-qiankunmu-Project_CodeNet-896c9d36/hub/datasets--qiankunmu--Project_CodeNet_Python800_and_Java250/snapshots/c899fde44a77ba1cc14973ed3de064e4ff3aadc7/Project_CodeNet_Java250.tar.gz