diff --git a/lanqiao/series13sheng/retry_tb.py b/lanqiao/series13sheng/retry_tb.py
index 5e6c10f..f5728d6 100644
--- a/lanqiao/series13sheng/retry_tb.py
+++ b/lanqiao/series13sheng/retry_tb.py
@@ -67,27 +67,9 @@ def lcm(a, b):
     return a * b // math.gcd(a, b)
 
 
-def cal_prime_nums(n):
-    prime = [1] * (n + 1)
-    prime[0] = prime[1] = 0
-    for i in range(2, n + 1):
-        j = i * i
-        while j <= n:
-            prime[j] = 0
-            j += i
-
-    res = []
-    for idx, num in enumerate(prime):
-        if num:
-            res.append(idx)
-
-    return res
-
-
 ans = 2022040920220409
 check(ans)
 
-prime = cal_prime_nums(99)
 ans = 1
 product = 1
 for num, mod in nums:
diff --git a/utils/__init__.py b/utils/__init__.py
new file mode 100644
index 0000000..e69de29
diff --git a/utils/cal_prime.py b/utils/cal_prime.py
new file mode 100644
index 0000000..0ea31c0
--- /dev/null
+++ b/utils/cal_prime.py
@@ -0,0 +1,15 @@
+def cal_prime(n):
+    prime = [1] * (n + 1)
+    prime[0] = prime[1] = 0
+    for i in range(2, n + 1):
+        j = i * i
+        while j <= n:
+            prime[j] = 0
+            j += i
+
+    res = []
+    for idx, num in enumerate(prime):
+        if num:
+            res.append(idx)
+
+    return res