/in/foo.cc: In function 'int main()':
/in/foo.cc:24:6: warning: unused variable 'step' [-Wunused-variable]
  int step = 0;
      ^~~~
/in/foo.cc:28:28: warning: 'num1' may be used uninitialized in this function [-Wmaybe-uninitialized]
  if ( num[ k - 1 ] == num1 || num[ j ] == num1 )
       ~~~~~~~~~~~~~~~~~~~~~^~~~~~~~~~~~~~~~~~~