/in/foo.cc: In function 'int main()':
/in/foo.cc:15:25: error: 'rows' was not declared in this scope
     for (int i = 0; i < rows; ++i) {
                         ^~~~
/in/foo.cc:16:29: error: 'cols' was not declared in this scope
         for (int j = 0; j < cols; ++j) {
                             ^~~~