#include <iostream>
#include <iomanip>
#include <algorithm>
#include <cstring>
#include <cstdio>
#include <cmath>
#include <map>
#include <stack>
#include <queue>
#include <sstream>
#define INF 0x3f3f3f3f
using namespace std;

typedef long long ll;
const int mod = 1e9 + 7;
const ll maxn = 1000005;
const double pi = acos(-1.0);

char s[maxn];

int main()
{
    while(cin >> s)
    {
        int vis[30];
        memset(vis,0,sizeof(vis));
        for(int i = 0; i < 4; i ++)
        {
            vis[s[i] - 65] ++;
        }
        int num = 0;
        for(int i = 0; i < 26; i ++)
        {
            if(vis[i] != 0)
                num ++;
        }
        if(num == 2)
            cout << "Yes" << endl;
        else
            cout << "No" << endl;
    }
    return 0;
}