text: Realiza la operación (a^b) % mod.
  
  /// O(1), 0 <= a, b < m
  ll mulmod(ll a, ll b, ll m) {
  	ll r = a*b-(ll)((long double)a*b/m+.5)*m;
  	return r < 0 ? r+m : r;
  }
  /// O(log(e)), 0 <= b < m
  ll expmod(ll b, ll e, ll m) {
      if (e == 0) return 1;
      if (e&1) return mulmod(b, expmod(b, e-1, m), m);
      b = expmod(b, e>>1, m);
      return mulmod(b, b, m);
  }
  