75分求助

#include <bits/stdc++.h>
using namespace std;
namespace IO{
    inline __int128 read(){
        register __int128 x = 0,f = 1;
        register char ch = getchar();
        while(ch<'0'||ch>'9'){
            if(ch=='-'){
                f = -1;
            }
            ch = getchar();
        }
        while(ch>='0'&&ch<='9'){
            x = x * 10 + ch - '0';
            ch = getchar();
        }
        return x*f;
    }
    inline void write(__int128 x){
        if(x<0){
            putchar('-');
            x = -x;
        }
        register int n = 0;
        char s[100];
        while(x||!n){
            s[n++] = '0' + x % 10;
            x /= 10;
        }
        while(n--){
            putchar(s[n]);
        }
        return;
    }
}
using namespace IO;
int main(){
    __int128 a[1000], b = 0, n;
    n = read();
    a[1] = 1;
    for(int i=2;i<=n+1;i++){
        a[i] = a[i-1] * i;
    }
    for(int i=1;i<=n;i++){
        b = b + a[i];
    }
    write(b);
    return 0;
}