#1508. 【CSP七连测Day1】上海

https://sjzezoj.com/submission/56127

S2OJ/1508/1508.cpp

@@ -0,0 +1,57 @@
+#include <iostream>
+#include <algorithm>
+#include <cmath>
+
+using std::cin;
+using std::cout;
+const char endl = '\n';
+
+const int N = 1e6 + 5;
+
+long long k, _k, cnt, p[N], c[N], ans = 1;
+bool flag;
+
+long long binpow(long long a, long long b) {
+    long long res = 1;
+
+    while (b) {
+        if (b & 1) res *= a;
+        a *= a;
+        b >>= 1;
+    }
+
+    return res;
+}
+
+int main() {
+    std::ios::sync_with_stdio(false);
+    cin.tie(nullptr);
+
+    cin >> k;
+
+    _k = k;
+
+    for (long long i = 2; i * i <= k; i++) {
+        if (k % i == 0) {
+            p[++cnt] = i;
+
+            while (k % i == 0) {
+                k /= i;
+                c[cnt]++;
+            }
+        }
+    }
+
+    if (k) {
+        p[++cnt] = k;
+        c[cnt] = 1;
+    }
+
+    for (int i = 1; i <= cnt; i++) {
+        ans *= binpow(p[i], static_cast<long long>(std::ceil(static_cast<long double>(c[i]) / 2)));
+    }
+
+    cout << (ans % _k ? ans : -1) << endl;
+
+    return 0;
+}