/in/foo.cc:32:22: warning: suggest parentheses around '+' inside '<<' [-Wparentheses]
 const int maxn=(1<<17+1)+5;
                    ~~^~
/in/foo.cc: In function 'void solve()':
/in/foo.cc:36:29: warning: suggest parentheses around '-' inside '<<' [-Wparentheses]
  int len=(1<<n)-1,half=(1<<n-1);
                            ~^~