#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 sxm(int x){ if(x==1)return 1; else return sxm(x-1)*x; } int main(){ int n,sum=0; cin>>n; sum+=sxm(n); cout<<sum<<endl; return 0; }