'commit'

TangDou/LanQiaoBei/LanQiao12XuanBaSai/3.cpp

@@ -0,0 +1,23 @@
+#include <bits/stdc++.h>
+
+using namespace std;
+
+//判断一个数是不是质数
+bool isPrime(int n) {
+    if (n < 2) return false;
+    for (int i = 2; i <= n / i; i++)
+        if (n % i == 0) return false;
+    return true;
+}
+
+int ans;
+
+int main() {
+    int n;
+    cin >> n;
+    for (int i = 7; i <= n; i++)
+        if (i % 10 == 7 && isPrime(i)) ans++;
+
+    cout << ans << endl;
+    return 0;
+}