From 8f9c6e307f329b6df1dd1b3484820fef6ceb7461 Mon Sep 17 00:00:00 2001
From: Baoshuo <i@baoshuo.ren>
Date: Wed, 13 Apr 2022 16:50:59 +0800
Subject: [PATCH] =?UTF-8?q?202.=20=E6=9C=80=E5=B9=B8=E8=BF=90=E7=9A=84?=
 =?UTF-8?q?=E6=95=B0=E5=AD=97?=
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https://www.acwing.com/problem/content/submission/code_detail/13373247/
---
 AcWing/202/202.cpp    | 54 +++++++++++++++++++++++++++++++++++++++++++
 AcWing/202/data/3.ans |  3 +++
 AcWing/202/data/3.in  |  3 +++
 3 files changed, 60 insertions(+)
 create mode 100644 AcWing/202/202.cpp
 create mode 100644 AcWing/202/data/3.ans
 create mode 100644 AcWing/202/data/3.in

diff --git a/AcWing/202/202.cpp b/AcWing/202/202.cpp
new file mode 100644
index 00000000..084f335e
--- /dev/null
+++ b/AcWing/202/202.cpp
@@ -0,0 +1,54 @@
+#include <algorithm>
+#include <iostream>
+#include <limits>
+
+using std::cin;
+using std::cout;
+const char endl = '\n';
+
+int t;
+long long l;
+
+long long euler(long long x) {
+    long long r = x;
+    for (long long i = 2; i * i <= x; i++) {
+        if (x % i == 0) {
+            r = r / i * (i - 1);
+            while (x % i == 0) x /= i;
+        }
+    }
+    if (x > 1) r = r / x * (x - 1);
+    return r;
+}
+
+long long binpow(__int128 a, long long b, long long m) {
+    a %= m;
+    __int128 res = 1;
+    while (b > 0) {
+        if (b & 1) res = res * a % m;
+        a = a * a % m;
+        b >>= 1;
+    }
+    return res;
+}
+
+int main() {
+    std::ios::sync_with_stdio(false);
+
+    while (cin >> l, l) {
+        long long d = std::__gcd(l, 8ll);
+        long long n = euler(9ll * l / d);
+        long long ans = std::numeric_limits<long long>::max();
+
+        for (long long i = 1; i * i <= n; i++) {
+            if (n % i == 0) {
+                if (binpow(10, i, 9ll * l / d) == 1) ans = std::min(ans, i);
+                if (binpow(10, n / i, 9ll * l / d) == 1) ans = std::min(ans, n / i);
+            }
+        }
+
+        cout << "Case " << ++t << ": " << (ans == std::numeric_limits<long long>::max() ? 0 : ans) << endl;
+    }
+
+    return 0;
+}
diff --git a/AcWing/202/data/3.ans b/AcWing/202/data/3.ans
new file mode 100644
index 00000000..3958e6d6
--- /dev/null
+++ b/AcWing/202/data/3.ans
@@ -0,0 +1,3 @@
+version https://git-lfs.github.com/spec/v1
+oid sha256:c5a2734e5a6c3a45f348713f8019fa4c2b3555667044ad719b9a90ab292651ec
+size 53
diff --git a/AcWing/202/data/3.in b/AcWing/202/data/3.in
new file mode 100644
index 00000000..a04c97d1
--- /dev/null
+++ b/AcWing/202/data/3.in
@@ -0,0 +1,3 @@
+version https://git-lfs.github.com/spec/v1
+oid sha256:0e39320a6bf2989bbab84f484275b6a3907869b917453eca1e6614520cd816a7
+size 35