int findLonelyPixel(vector<vector<char>>& picture) {

int result = 0;

int n = (int)picture.size();

int m = (int)picture[0].size();

vector<bool> col(m, true);

for(int i = 0; i < n; i++) {

for(int j = 0; j < m; j++) {

if(col[j]) {

if(picture[i][j] == 'B') {

int k = 0;

for(k = 0; k < n; k++) {

if(k != i and picture[k][j] != 'W') {

break;

}

}

if(k == n) {

k = 0;

for(k = j + 1; k < m; k++) {

if(picture[i][k] != 'W') {

break;

}

}

}

if(k == m) {

result++;

}

col[j] = false;

break;

}

}

}

}

return result;

}