#include<iostream> // cin\cout\endl #include<cstdio> //scanf()\printf() #include<cstring> // strcpy()\strcat()\strcmp()\strlen()\memset() #include<cmath> //sqrt()\pow()\abs()\ceil()\floor()\max()\min() using namespace std; /* int a(int x,int y){ int sum=0; for(int i=x;i<=y;i++){ sum+=i; } return sum; } int main(){ cout<<a(1,10)<<endl; cout<<a(20,30)<<endl; cout<<a(35,45)<<endl; return 0; } */ int a(int x){ int sum=1; for(int i=1;i<=x;i++) sum*=i; return sum; } int main(){ int n,s=0; cin>>n; for(int j=1;j<=n;j++){ s+=a(j); } cout<<s; return 0; }