diff --git a/template.cc b/template.cc
index 55e1bc6..dd9e423 100644
--- a/template.cc
+++ b/template.cc
@@ -286,6 +286,7 @@ inline ll root(ll n, ll i) {
 #define comb(n, k) ((n) < 0 or (k) < 0 or (n) < (k) ? 0 : fact[n] / fact[k] / fact[(n) - (k)])
 #define fastcomb(n, k) ((n) < 0 or (k) < 0 or (n) < (k) ? 0 : fact[n] * factrev[k] * factrev[(n) - (k)])
 
+__attribute__((target("lzcnt")))
 constexpr inline int lg2(ll x) { return x == 0 ? -1 : sizeof(ll) * 8 - 1 - __builtin_clzll(x); }
 
 template <typename T>