/in/foo.cc: In function 'int main()':
/in/foo.cc:6:12: warning: unused variable 'a' [-Wunused-variable]
  int n,m=0,a,s;
            ^
/in/foo.cc:6:14: warning: 's' may be used uninitialized in this function [-Wmaybe-uninitialized]
  int n,m=0,a,s;
              ^