Go: package main

import (
	"bufio"
	"fmt"
	"os"
	"strconv"
)

var scanner = bufio.NewScanner(os.Stdin)

func nextString() string {
	scanner.Scan()
	return scanner.Text()
}

func nextInt() int {
	n, err := strconv.Atoi(nextString())
	if err != nil {
		fmt.Printf("strconv.Atoi failed: %v\n", err)
	}
	return n
}

func main() {
	scanner.Split(bufio.ScanWords)

	n := nextInt()
	f := 1
	for i := 1; i <= n; i++ {
		f *= i
	}
	fmt.Println(f)
}

C++: #include <iostream>

using namespace std;

int fact(int n) {
    return (n == 1) ? 1 : n * fact(n - 1);
}

int main()
{
    int n;
    int sum = 0;
    
    while (cin >> n) {
        cout << fact(n) << endl;
    }

    return 0;
}

C++: #include <iostream>
using namespace std;
 
int main()
{
    int n; 
    long long int ans = 1;
    cin >> n;
    while(n > 0){
        ans *= n;
        n--;
    }
    cout << ans << endl;
}

C++: #include <iostream>
using namespace std;

#define ULL_INT unsigned long long int

int main() {
	int n; cin >> n; ULL_INT ans = 1;
	for (int i = n; i > 0; i--) ans *= i;
	cout << ans << endl;
	return 0;
}

C++: #include <iostream>
using namespace std;

int main(int argc, char **argv)
{
 int n, tmp;
 cin >> n;
 tmp = 1;
 while(n > 1){
  tmp *= n;
  n--;
 }
 cout << tmp;
 return 0;
}

C++: #include <bits/stdc++.h>
using namespace std;
int fact(int num){
	if(num==0) return 1;
	return num*fact(num-1);
}
int main(){
	unsigned long long n =0;
	cin>>n;
	n = fact(n);
	cout<<n<<endl;
	return 0;
}

C++: #include <iostream>

unsigned Factorial(unsigned n)
{
	int ans=n;
	while(--n>0)
	{
		ans *= n;
	}
	return ans;
}

int main()
{
	unsigned n;
	std::cin >> n;

	std::cout << Factorial(n) << '\n';
}

C++: #include<bits/stdc++.h>
using namespace std;
int main()
{
    //freopen("in.txt","r",stdin);
    ios::sync_with_stdio(false);
    long long int n,i,fac=1;
    cin >> n;
    for(i=n; i>0; i--)
        fac*=i;
    cout << fac << endl;
    return 0;
}

C++: #include <iostream>
using namespace std;

long long factorial(int n) {
	if (n == 0) {
		return 1;
	}
	else {
		return n * factorial(n-1);
	}
}

int main() {
	int n;
	cin >> n;
	cout << factorial(n) << endl;
}

C++: #include<iostream>
#include<stdio.h>

using namespace std;

int factorial(int n) {

	return (n > 0 ? n*factorial(n - 1) : 1);

}

int main() {
	int n;
	scanf("%d", &n);
	
	printf("%d \n", factorial(n));

	return 0;
}

C++: #include <iostream>
using namespace std;

int main()
{
	int n;
	long long int ans = 1;
	int num;

	cin >> n;

	for(int i = n+1; i>1; i--)
	{
		ans *= (i-1);
	}

	cout << ans << endl;

	return 0;
}

C++: #include <iostream>

using namespace std;

int main()
{
    long long fact[21] = {};
    fact[0] = 1;
    int a; cin >> a;
    for (int i = 1; i <= a; ++i) fact[i] = i * fact[i - 1];
    cout << fact[a] << endl;
}

C++: #include <iostream>
#include <cstdlib>
#include <windows.h>
using namespace std;

int main()
{
    long long n;
    
    do
    {
    cin >> n;
    
    }while(n>20);
    
    int x;
    long long sum=1;
    for(x=1; x<=n; x++)
    {
       sum = sum*x;
    }
    
    cout<< sum << endl;
    
    return 0;
}

C++: #include<iostream>
using namespace std;
int main(){
	int n;
	cin>>n;
	long long sum=1;
	for(int i=2;i<=n;i++){
		sum*=i;
	}
	cout<<sum;
}

C++: #include <iostream>
using namespace std;

int main() {
	int n,a;
	cin>>n;
	a = n;
	while(true){
		n = n-1;
		if (n == 0)break;
		a = a*n;
	}cout<<a<<endl;
}

C++: #include <stdio.h>
int fact(int n){ return n>1 ? fact(n-1)*n : 1; }
int main(){
  int n;
  while(~scanf("%d",&n)){
    printf("%d\n",fact(n));
  }
  return 0;
}

C++: //include
//------------------------------------------
#include <vector>
#include <list>
#include <map>
#include <set>
#include <deque>
#include <stack>
#include <bitset>
#include <algorithm>
#include <functional>
#include <numeric>
#include <utility>
#include <sstream>
#include <iostream>
#include <iomanip>
#include <queue>
#include <iterator>
#include <cstdio>
#include <cmath>
#include <cstdlib>
#include <cctype>
#include <string>
#include <cstring>
#include <ctime>

using namespace std;

//conversion
//------------------------------------------
inline int toInt(string s) {int v; istringstream sin(s);sin>>v;return v;}
template<class T> inline string toString(T x) {ostringstream sout;sout<<x;return sout.str();}

//math
//-------------------------------------------
template<class T> inline T sqr(T x) {return x*x;}

//typedef
//------------------------------------------
typedef vector<int> VI;
typedef vector<VI> VVI;
typedef vector<string> VS;
typedef pair<int, int> PII;
typedef long long LL;

//container util
//------------------------------------------
#define ALL(a)  (a).begin(),(a).end()
#define RALL(a) (a).rbegin(), (a).rend()
#define PB push_back
#define MP make_pair
#define SZ(a) int((a).size())
#define EACH(i,c) for(typeof((c).begin()) i=(c).begin(); i!=(c).end(); ++i)
#define EXIST(s,e) ((s).find(e)!=(s).end())
#define SORT(c) sort((c).begin(),(c).end())

//repetition
//------------------------------------------
#define FOR(i,a,b) for(int i=(a);i<(b);++i)
#define REP(i,n)  FOR(i,0,n)

//constant
//--------------------------------------------
const double EPS = 1e-10;
const double PI  = acos(-1.0);

//clear memory
#define CLR(a) memset((a), 0 ,sizeof(a))

//debug
#define dump(x)  cerr << #x << " = " << (x) << endl;
#define debug(x) cerr << #x << " = " << (x) << " (L" << __LINE__ << ")" << " " << __FILE__ << endl;

int gcd(int a, int b){
   int tmp;
   while(a%b==0){
      tmp=a%b;
      a=b;
      b=tmp;
   }
}

int lcm(int a,int b){
   return a*b/gcd(a,b);
}

bool prime_number(int n){
   if(n < 2){
      return false;
   }
   else if(n == 2){
      return true;
   }
   if(n % 2 == 0){
      return false;
   }
   for(int i=3;i<=n/i;i+=2){
      if(n % i == 0) return false;
      return true;
   }
}

int main(){
   int a,ans=1;
   cin >> a;
   for(int i=1;i<=a;i++) ans*=i;
   cout << ans << endl;
}

C++: #include <iostream>

int main(){
long long int ans = 1;
int n;
cin >> n;
for(int i=1; i<=n; i++)
ans*=i;
cout << ans << endl;

return 0;
}

C++: #include<cstdio>

long long int factorial(int n){
	if(n == 1) return 1;
	return n * factorial(n - 1);
}

int main(){
	int n;
	scanf("%d", &n);
	printf("%lld\n", factorial(n));
	return 0;
}

C++: #include <iostream>
using namespace std;

int factorial(int n){
  if(n > 0){
    return n*factorial(n-1);
  } else {
    return 1;
  }
}

int main(){
  int n;
  cin>>n;
  // if(n<1||n<20)return 0;
  cout<< factorial(n)<<endl;
}

C++: #include <cstdio>
using namespace std;

typedef long long int LLI;

LLI n;
LLI ans = 1;

int main() {
  scanf("%lld", &n);
  while (n > 0) {
    ans *= n;
    --n;
  }

  printf("%lld\n", ans);
}

C++: #include <iostream>
using namespace std;

int main() {
int n,sum=1;
cin>>n;
for(int k=1;k<=n;k++){
	sum=sum*k;
}
cout<<sum;

	return 0;
}

C++: #include <iostream>
#include <stdio.h>
#include <string.h>
#include <math.h>
#include <algorithm>
#include <stdlib.h>
#include <vector>

using namespace std;


int main(){

	int n;
	cin >> n;

	int sum=1;

	for(int i=n; i>0 ; i--){
		sum *= i;
	}

	cout << sum << endl;
	return 0;
}

C++: #include <iostream>
using namespace std;

int main()
{
	int x;
	unsigned int ret=1;
	cin >> x;
	for(int i=1;i<=x;i++)
		ret*=i;
	if(!x)ret=0;
	cout << ret << endl;
}

C++: #include<iostream>
using namespace std;

int main(){
	int n;
	long long int ans = 1;
	cin >> n;
	while(n){
		ans *= n;
		n--;
	}
	cout << ans << endl;
}

C++: #include <iostream>
#include <cstdio>

using namespace std;

int main() {
  while(!feof(stdin)) {
    int n, sum=1;
    scanf("%d", &n);
    if (feof(stdin)) break;
    for(int i=1;i<=n;i++)
      sum*=i;
    printf("%d\n", sum);
  }
}