/in/foo.cc: In function 'int main()':
/in/foo.cc:99:17: warning: suggest parentheses around comparison in operand of '&' [-Wparentheses]
   a[i] = (i & 1 == 1) ? mod - inv[i] : inv[i];
               ~~^~~~
/in/foo.cc:104:47: error: could not convert '(ll*)(& a)' from 'll* {aka long long int*}' to 'Polynomial'
  cout << quick_mul(a, b, limit/*, mod, mod_g*/).a[m] * t % mod;
                                               ^