/in/foo.c: In function 'main':
/in/foo.c:9:2: warning: statement with no effect [-Wunused-value]
  for(x; x > b/2; x--) 
  ^~~
/in/foo.c:10:3: warning: statement with no effect [-Wunused-value]
  {for(j; j < x -  1 ; j++) a[i][j] = n++;
   ^~~
/in/foo.c:11:2: warning: statement with no effect [-Wunused-value]
  for(i; i < x -  1 ; i++) a[i][j] = n++;
  ^~~
/in/foo.c:12:2: warning: statement with no effect [-Wunused-value]
  for(j; j > m; j--) a[i][j] = n++;
  ^~~
/in/foo.c:13:2: warning: statement with no effect [-Wunused-value]
  for(i; i > m; i--) a[i][j] = n++;
  ^~~