/in/foo.cc:20:0: warning: "maxn" redefined
 #define maxn 2000005
 
/in/foo.cc:17:0: note: this is the location of the previous definition
 #define maxn  560050  
 
/in/foo.cc: In function 'll dfs(ll, ll, ll, ll)':
/in/foo.cc:31:18: warning: unused variable 'j' [-Wunused-variable]
  ll ans, num, i, j;
                  ^
/in/foo.cc: In function 'int main()':
/in/foo.cc:58:11: warning: unused variable 'i' [-Wunused-variable]
  ll a, b, i, j, ans1 = 0, ans2 = 0;
           ^
/in/foo.cc:58:14: warning: unused variable 'j' [-Wunused-variable]
  ll a, b, i, j, ans1 = 0, ans2 = 0;
              ^