/in/foo.cc: In function 'LL solve(int, int, int, LL)':
/in/foo.cc:29:5: warning: unused variable 'sum' [-Wunused-variable]
  LL sum = 0;
     ^~~
/in/foo.cc:30:9: warning: unused variable 'j' [-Wunused-variable]
  int i, j, l;
         ^