#include<bits/stdc++.h>
using namespace std;const unsigned N=2e5+1;
#define void inline void
#define int register unsigned
#define ge getchar()
inline long double aa(int n){long double ans=1;for(int i=2;i<=n;++i)ans*=i;return ans;}
signed main(){ios::sync_with_stdio(0);long double ans=0;
    int n=0;register char c=ge^48;n=c;c=ge;if(c<59&&c>47)n=n*10+c-48;
    for(int i=1;i<=n;++i)ans+=aa(i);printf("%.0Lf",ans);	
}

正解输出：

31035053229546199656252032972759319953190362094566672920420940313

我的输出：

31035053229546199652450892297664579467066897756393885159194099712

从第20位开始不一样