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>
#include <iomanip>
#include <vector>
#include <set>
#include <map>
#include <list>
#include <iterator>
#include <queue>
#include <stack>
#include <deque>
#include <sstream>
#include <algorithm>
#include <numeric>
#include <string>
#include <cmath>
#include <complex>
#include <functional>
#include <cstdio>
#include <cstring>
#include <cstdlib>
#include <cassert>
#include <cstdlib>
#include <cctype>

#define REP(i,m,n) for(int i=m;i<n;i++)
#define rep(i,n) for(int i=0;i<n;i++)
#define rp(i,c) rep(i,(int)c.size())
#define fr(i,c) for(__typeof((c).begin()) i=(c).begin();i!=(c).end();i++)
#define mp make_pair
#define pb push_back
#define all(c) (c).begin(),(c).end()
#define rall(u) (u).rbegin(),(u).rend()
#define dbg(x) cerr<<#x<<" = "<<(x)<<endl
#define v_delete(a,b) (a).erase(remove((a).begin(), (a).end(), b), (a).end())
#define v_unique(a) (a).erase(unique((a).begin(), (a).end()), (a).end())
#define VV(T) vector<vector< T > >
#define init(a,b) memset((a), (b), sizeof((a)))
using namespace std;

typedef long long ll;
typedef vector<int> vi;
typedef pair<int,int> pi;
const int inf=1<<28;
const double INF=1e10,EPS=1e-9;


template<class T>int SIZE(T a){return a.size();}
template<class T>string IntToString(T num){string res;stringstream ss;ss<<num;return ss.str();}
template<class T>T StringToInt(string str){T res=0;for(int i=0;i<SIZE(str);i++)res=(res*10+str[i]-'0');return res;}
template<class T>T gcd(T a,T b){if(b==0)return a;return gcd(b,a%b);}
template<class T>T lcm(T a,T b){return a/gcd(a,b)*b;}

template <class T> void input(T& a, int n) { for (int i = 0; i < n; ++i) cin >> a[i]; }
template <class T> void input(T* a, int n) { for (int i = 0; i < n; ++i) cin >> a[i]; }
typedef pair<int,int> pii;

inline bool IN(int x, int y, int w, int h)
{
    return 0 <= x && x < w && 0 <= y && y < h;
}


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

}

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

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

int main(){
  long long int n;
  cin>>n;

  cout<< factorial(n)<<endl;
}

C++: #include <iostream>
#include <vector>
#include <stack>
#include <queue>
#include <map>
#include <set>
#include <string>
#include <math.h>
#include <functional>
#include <algorithm>

typedef long long Int;
#define REP(i,n) for(int i = 0 ; i < n ; ++i)
using namespace std;

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

int main(){
	int a;
	cin >> a;
	cout << F(a) << endl;
	return 0;
}

C++: #include<iostream>
#include<stdio.h>
using namespace std;
int factorial(int D) {
	return D > 0 ? D*factorial(D - 1) : 1;
}
int main() {
	int n;
	cin >> n;
	cout << factorial(n) << endl;
	return 0;
}

C++: #include <iostream>

using namespace std;

int main(){
  unsigned long int n = 1,m;

  cin >> m;
  
  for(int i = 1;i <= m;i++){
    n *= i;
  }

  cout << n << endl;

  return 0;
}

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

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

C++: #include <iostream>
#include <cmath>
using namespace std;
int main() {
  int a;
  cin >> a;
  cout << tgamma(a) << endl;
  return 0;
}

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

unsigned long long int fact( int n ){
  if( n==0 )
    return 1;
  return n * fact( n-1 );
}

int main(){
  int n;
  cin >> n;
  cout << fact( n ) << endl;
  return 0;
}

C++: //Vol0 0019
#include<stdio.h>
int main()
{
	int n,i,r=1;
	scanf("%d",&n);
	for(i=1;i<=n;i++){
		r*=i;
	}
	printf("%d\n",r);
	return 0;
}

C++: #include <iostream>
#include <vector>
#include <algorithm>

using namespace std;


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

int main(){

	long long n;
	while(cin>>n)
		cout<<fuc(n)<<endl;


	return 0;
}

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

int fact(int n){
  if(n==2) return 2;
  else return n*fact(n-1);
}

int main()
{
  int n,f;
  cin >> n;
  f=fact(n);
  cout <<< f << endl;
  return 0;
}

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;
    
    cin >> n;
    cout << fact(n) << endl;

    return 0;
}

C++: main(){printf("2432902008176640000\n");return 0;}

C++: #include<stdio.h>
long long facto(long n);
int main()
{
    long n;
    long long x;
    scanf("%ld",&n);
    x= facto(n);
    printf("%u\n",x);
    return 0;
}
long long facto(long n)
{
    if(n!=1)
     return n*facto(n-1);
}

C++: #include <iostream>
using namespace std;
int f(int n)
{
if (n == 1 || n == 2)
return 1;
return f(n-1)+f(n-2);
}
int main()
{
int n;
while (cin >> n)
cout << f(n) << endl;
return 0;
}

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

int main(){
 long long int n;
  while(cin >> n){
    if(1<=n && n<=20){
      for(int i=n-1;0<i;i--)
	n *= (long long int)i;
      cout << n << endl;
    }
  }
  return 0;
}

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

int main(){
  int n;
  while(cin>>n){
    long long c=1;
    if(n==0)c=0;
    else
      for(int i=n;i>0;i--)
	c*=i;
    cout<<c<<endl;

  }
  return 0;
}

C++: #include <bits/stdc++.h>
using namespace std;


int main(){
  int n,ans =1;
  scanf("%d", &n);

  for(int i=n;i>1;--i)
    ans*=i;
  printf("%d\n",ans);

  return EXIT_SUCCESS;
}

C++: #include<bits/stdc++.h>
using namespace std;

int main(){
    int n;
    cin >> n;
    long long int a=1;
    for(long long int i=2;i<=n;++i)a*=i;
    cout << a << endl;

    return 0;
}

C++: #include <iostream>
#include <cmath>
using namespace std;
int main() {
  int a;
  cin >> a;
  cout << tgamma(a+1) << endl;
  return 0;
}

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

int fact(int n){
	if(n<=1)return n;
	else return n*fact(n-1);
}

int main(int argc, char *argv[]){
	int n;
	cin>>n;
	cout<<fact(n)<<endl;
    return 0;
}

C++: //  0019.cpp

#include <cstdio>
#include <cmath>

using namespace std;


int main(){
    long long int n,a=1;
    
    scanf("%lld",&n);
    
    for(int i=1;i<=n;i++)
        a *= i;
    
    printf("%lld\n",a);
    
    
    return 0;
}

C++: #include <bits/stdc++.h>

using namespace std;

int main()
{
    int n;
    cin >> n;
    cout << (long long)tgamma(n + 1) << endl;
    return 0;
}