#include <iostream>
#include <vector>
using namespace std;
int main(){
    vector<vector<char>> A(3,vector<char>(3));
    for(int i = 0; 3 > i; i++){
        for(int j = 0; 3 > j; j++){
            cin>>A[i][j];
        }
    }
    for(int i = 0; 3 > i; i++){
        for(int j = 0; 3 > j; j++){
            if(A[i][j] != (((i+j)%2 ? A[0][1] : A[0][0]))){
                cout << "No" << endl;
                return 0;
            }
        }
    }
    if(A[0][1] == A[0][0])cout << "No" << endl;
    else cout << "Yes" << endl;
}