/in/foo.cc: In function 'int main()':
/in/foo.cc:10:10: warning: statement has no effect [-Wunused-value]
   int b;b<=n;b++;
         ~^~~
/in/foo.cc:10:17: warning: 'b' may be used uninitialized in this function [-Wmaybe-uninitialized]
   int b;b<=n;b++;
                 ^
/in/foo.cc:8:2: warning: 'a' may be used uninitialized in this function [-Wmaybe-uninitialized]
  for(int a;a<=n;a++)
  ^~~