/in/foo.c:3:1: warning: return type defaults to 'int' [-Wimplicit-int]
 main()
 ^~~~
/in/foo.c: In function 'main':
/in/foo.c:11:9: warning: 'r' may be used uninitialized in this function [-Wmaybe-uninitialized]
   r = r * 10 + b;
       ~~^~~~