/in/foo.cc: In function 'void merge(int*, int*, int)':
/in/foo.cc:21:17: warning: unused variable 'cnt' [-Wunused-variable]
  int i, l1, l2, cnt = 0;
                 ^~~
/in/foo.cc: In function 'int main()':
/in/foo.cc:30:27: warning: unused variable 'm' [-Wunused-variable]
  int ans = 0, i, j, v, n, m, a, b;
                           ^