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#include <iostream>
#include <cmath>
#include <vector>
#include <algorithm>
using namespace std;
int main() {
	char a[4][4],flag = 1;
	for (int i = 0; i < 4; i++){
		for (int j = 0; j < 4; j++){
			cin >> a[i][j];
		}
	}
	for (int i = 0; i < 3; i++){
		for (int j = 0; j < 3; j++)
		{
			if (a[i][j] == a[i][j + 1] && a[i + 1][j] == a[i + 1][j + 1] && a[i][j] == a[i + 1][j]) {
				flag = 0;
			}
		}
	}
	if (flag) cout << "Yes";
	else cout << "No";
}