11 lines
291 B
C++
11 lines
291 B
C++
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#include <bits/stdc++.h>
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using namespace std;
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//公式！重要的是公式！
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int main() {
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ios::sync_with_stdio(false); //读入输出优化的强迫症
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unsigned long long n;
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cin >> n;
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cout << (n * (n - 1) / 2 * (n - 2) / 3 * (n - 3) / 4) << endl;
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return 0;
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}
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