/in/foo.c: In function 'xy4':
/in/foo.c:12:13: warning: unused variable 'i' [-Wunused-variable]
       int m,i;
             ^
/in/foo.c: At top level:
/in/foo.c:30:1: warning: return type defaults to 'int' [-Wimplicit-int]
 main()
 ^~~~
/in/foo.c: In function 'xy4':
/in/foo.c:29:1: warning: control reaches end of non-void function [-Wreturn-type]
 }
 ^
/in/foo.c: In function 'main':
/in/foo.c:81:13: warning: 'k' may be used uninitialized in this function [-Wmaybe-uninitialized]
         S[k]=1;
         ~~~~^~