/in/foo.cc: In function 'int main()':
/in/foo.cc:4:8: warning: unused variable 'm' [-Wunused-variable]
  int n,m,a=0,sum=0;
        ^
/in/foo.cc:4:10: warning: unused variable 'a' [-Wunused-variable]
  int n,m,a=0,sum=0;
          ^
/in/foo.cc:4:14: warning: unused variable 'sum' [-Wunused-variable]
  int n,m,a=0,sum=0;
              ^~~