Updated in response to comments

Author: Chillee

content/number-theory/ModularArithmetic.h

@@ -28,5 +28,5 @@ struct Mod {
 		Mod r = *this ^ (e / 2); r = r * r;
 		return e&1 ? *this * r : r;
 	}
-	operator ll(){ return x; }
+	explicit operator ll(){ return x; }
 };

content/numerical/FFTPolynomial.h

@@ -107,9 +107,10 @@ poly exp(poly a) {
     return modK(b, sz(a));
 }
 poly pow(poly a, ll m) {
-    int p = 0; int n = sz(a);
+    int p = 0, n = sz(a);
     while (p < sz(a) && a[p].x == 0)
         ++p;
+    if (ll(m)*p >= sz(a)) return poly(sz(a));
     num j = a[p];
     a = {a.begin() + p, a.end()};
     a = a * (num(1) / j);