'commit'

TangDou/AcWing_TiGao/T5/RongChi/HDU3501_2.cpp

@@ -0,0 +1,46 @@
+#include <bits/stdc++.h>
+using namespace std;
+long long fac[500];
+int cnt;
+void fen(int n) {
+    for (int i = 2; i * i <= n; i++) {
+        if (n % i == 0) {
+            fac[cnt++] = i;
+            while (n % i == 0) n /= i;
+        }
+    }
+    if (n > 1) fac[cnt++] = n;
+} //素因子分解
+long long ans;
+int n;
+const int mod = 1000000007;
+void dfs(int w, int id, long long sum) {
+    for (int i = w; i < cnt; i++) {
+        long long ss = sum * fac[i];
+        if (id & 1) {
+            int tmp = n / ss;
+            ans += ss * (1 + tmp) * tmp / 2;
+            ans %= mod;
+        } else {
+            int tmp = n / ss;
+            ans -= ss * (1 + tmp) * tmp / 2;
+            ans = (ans + mod) % mod;
+        }
+        dfs(i + 1, id + 1, ss);
+    }
+} //递归实现容斥原理
+int main() {
+    while (scanf("%d", &n) != EOF) {
+        if (n == 0) break;
+        if (n == 1) {
+            cout << 0 << endl;
+            continue;
+        }
+        cnt = 0;
+        fen(n);
+        ans = 0;
+        dfs(0, 1, 1);
+        cout << (ans % mod - n + mod) % mod << endl;
+    }
+    return 0;
+}