#include <bits/stdc++.h>
using namespace std;
int n, m;
vector<string> g;
bool canPhoto(char color)
{
vector<int> rowBad(n, 0), colBad(m, 0);
int total = 0;
for (int i = 0; i < n; i++)
for (int j = 0; j < m; j++)
if (g[i][j] != color)
{
rowBad[i]++;
colBad[j]++;
total++;
}
for (int i = 0; i < n; i++)
for (int j = 0; j < m; j++)
{
int removed = rowBad[i] + colBad[j];
if (g[i][j] != color)
removed--; // клітинка (i, j) була врахована двічі
if (removed == total)
return true;
}
return false;
}
int main()
{
cin >> n >> m;
g.resize(n);
for (int i = 0; i < n; i++)
cin >> g[i];
if (canPhoto('Y') || canPhoto('B'))
cout << "Yes\n";
else
cout << "No\n";
return 0;
}
