25 lines
476 B
C++
25 lines
476 B
C++
#include <bits/stdc++.h>
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using namespace std;
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typedef long long LL;
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const int mod = 1e9 + 7;
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// 快速幂
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int qmi(int a, int b) {
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int res = 1;
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while (b) {
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if (b & 1) res = (LL)res * a % mod;
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a = (LL)a * a % mod;
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b >>= 1;
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}
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return res;
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}
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int main() {
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LL n;
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cin >> n;
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LL a = (n * (n + 1)) % mod;
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a = a * (2 * n + 1) % mod;
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a = a * qmi(6, mod - 2) % mod;
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cout << a << endl;
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return 0;
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} |