题解：P12323 [蓝桥杯 2023 省 Java B] 阶乘求和

#include <bits/stdc++.h>
using namespace std;
long long s = 0, jc = 1;
long long MOD = 1e9;
int main() {
	for (int i = 2; i <= 50; i++) {
		s = (s + jc) % MOD;
		jc = (jc * i) % MOD;
	}
	cout << s;
	return 0;
}