```python
n=input()
n=int(n)
ans=0
ans=int(ans)
for i in range(1,n+1):
d=1
for j in range(1,i+1):
d*=j
ans+=d
print(ans)
```
by Viston @ 2018-09-14 21:27:49
py不算QAQ
by BuXiangJuanLe @ 2018-09-14 21:30:02
打表大法好
by 起名真的很难 @ 2018-09-14 21:39:14