/in/foo.cc: In function 'int main()':
/in/foo.cc:9:7: warning: unused variable 'j' [-Wunused-variable]
   int j=1;
       ^
/in/foo.cc:20:4: warning: 'n' may be used uninitialized in this function [-Wmaybe-uninitialized]
   n=n+b[i]*i;
   ~^~~~~~~~~