/in/foo.cc: In function 'int main()':
/in/foo.cc:8:16: warning: unused variable 'k' [-Wunused-variable]
  long n, i, j, k, tmp, x1, x2;
                ^
/in/foo.cc:8:19: warning: unused variable 'tmp' [-Wunused-variable]
  long n, i, j, k, tmp, x1, x2;
                   ^~~
/in/foo.cc:8:24: warning: unused variable 'x1' [-Wunused-variable]
  long n, i, j, k, tmp, x1, x2;
                        ^~
/in/foo.cc:8:28: warning: unused variable 'x2' [-Wunused-variable]
  long n, i, j, k, tmp, x1, x2;
                            ^~