/in/foo.cc: In function 'int main()':
/in/foo.cc:5:12: warning: unused variable 'a' [-Wunused-variable]
  int n,i,j,a,b,c;
            ^
/in/foo.cc:5:14: warning: unused variable 'b' [-Wunused-variable]
  int n,i,j,a,b,c;
              ^
/in/foo.cc:5:16: warning: unused variable 'c' [-Wunused-variable]
  int n,i,j,a,b,c;
                ^
/in/foo.cc:8:12: warning: 'n' may be used uninitialized in this function [-Wmaybe-uninitialized]
   for(j=1;j<=n;j++)
           ~^~~