Go: package main

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

var sc = bufio.NewScanner(os.Stdin)
func readInt() int64 {
    sc.Scan()
    n, _ := strconv.Atoi(sc.Text())
    return int64(n)
}


func main() {
    var ans int64 = 1
    var n int64 = readInt()
    var i int64
    for i = 1; i <= n; i++ {
        ans *= i
    }
    fmt.Println(ans)
}

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 <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;
typedef unsigned long long ULL;

//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 factrial(int n) {
  if(n == 1) return 1;
  else return n * factrial(n-1);
}

int main() {
  int n;

  cin >> n;

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

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

C++: #include <cstdio>

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

int main(int argc, char *argv[]) {
	int rcv;
	fscanf(stdin, "%d", &rcv);
	
	printf("%d\n", factorial(rcv));
	return 0;
}

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

int main() {
	ios :: sync_with_stdio(false);
	int n; cin >> n;
	int ans = 1;
	for(int i = 1; i <= n; i ++)
		ans *= i;
	cout << ans << '\n';
	return 0;
}

C++: #include <iostream>
#include <sstream>
#include <cstdio>
#include <cstdlib>
#include <cmath>
#include <cstring>
#include <string>
#include <vector>
#include <stack>
#include <queue>
#include <set>
#include <map>
#include <algorithm>
#include <functional>

using namespace std;

int main()
{
	long n, res = 1;

	cin >> n;

	for ( int i = 1; i <= n; i++ )
	{
		res *= i;
	}

	cout << res << endl;

	return 0;
}

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

int main()
{
 int n;
 long long int x;
 for(int i=1; i<=n; i++)
{
 x=n*i;
cout<<x<<endl;
}
return 0;
}

C++: #include <iostream>

using namespace std;

int main(int argc, char *argv[]) {
  int n, result;
  cin >> n;
  result = n;

  for (int i = 1; i < n; i++)
    result *= i;

  cout << result;
  return 0;
}

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

using namespace std;

int main()
{
	int n,ans = 1;

	scanf("%d",&n);
	for(int i = 2; i <= n; i++){
		ans *= i;
	}
	printf("%d\n",ans);

	return 0;
}

C++: #include <iostream>

int main(){
	int n,a=1;
	std::cin>>n;
	if(n<=20&&n>0){
	while(n!=0){
		a=a*n;
		n--;
	
	}
	
	std::cout<<a<<std::endl;
}
	return 0;
}

C++: #include<iostream>
using namespace std;
int main(){
	long long int n=0,x=1;
	cin>>n;
	for(int i=1;i<=n;i++){
		x=x*i;
	}
	cout<<x<<endl;
}

C++: #include <iostream>
#include <vector>
#include <utility>
#include <string>
#include <algorithm>
#include <numeric>
#include <cmath>
#include <string.h>
#include <deque>
#define REP(i,j,n) for(int i=j;i<n;i++)
#define SORT(x) sort(x.begin(),x.end())

using namespace std;



int main() {
	int n,sum=1;
	cin >> n;
	while (n > 1 ){
		sum *= n;
		n--;
	}

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

C++: #include <iostream>

int main(void)
{
  int n = 0;
  std::cin >> n;
  
  long long int fact = 1;
  
  for (int i = 1; i <= n; i++) {
    fact *= i;
  }
  
  std::cout << fact << std::endl;
  
  return 0;
}

C++: #include <iostream>
#include <iomanip>
#include <cstdio>
#include <cmath>
#include <cstring>
#include <algorithm>
#include <string>
#include <vector>
#include <stack>
#include <queue>
#include <set>
#include <map>
#include <sstream>
#include <complex>
#include <ctime>
#include <cassert>
#include <functional>
#include <list>
#include <bitset>
#include <cfenv>
#include <numeric>
#include <utility>
#include <cstdio>
#include <fstream>
#include <deque>
#include <limits>
#include <climits>
using namespace std;
typedef pair<int, int> ii;

int main() {
    ios::sync_with_stdio(false);

    long long n;

    cin >> n;

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

    cout << n << endl;

    return 0;
}

C++: #include <iostream>

using namespace std;

typedef long long ll;

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

    cout << ret << endl;
    return 0;
}

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

int main()
{
    int i,rslt=1, n;
    cin>>n;

    for(i=1;i<=n;i++){
        rslt*=i;


    }
    cout<<rslt<<endl;
    return 0;
}

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

int main()
{
	int i;
	int j;
	long long mul;
	bool stop=false;

	do
	{cin>>i;
	if(i>0 && i<=20)
	{
		mul=1;
	for (j=i;j>1;j--)
	{
		mul*=j;
	}

	cout<<mul<<endl;
	}
	if (i==0)
		cout<<"1"<<endl;
	}while(stop==false);

	return 0;
}

C++: #include<iostream>
using namespace std;
int fac(int x)
{
	int r = 1;
	for (int i = 1; i <= x; i++){
		r *= i;
	}
	return r;
}
int main()
{
	int n;
	while ((n <= 20) && (n >= 1)){
		cin >> n;
	}
	cout << fac(n) << endl;
	return 0;
}

C++: #include <iostream>

using namespace std;

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

	return n * factorial(n - 1);
}

int main()
{
	int n;

	cin >> n;

	cout << factorial(n) << endl;

	return 0;
}

C++: #include<bits/stdc++.h>
using namespace std;
int fun(int n){
if(n<=0)return 0;
if(n==1)return 1;
long int ret=n*fun(n-1);
return ret;
}
int main()
{
    long int n,answer;
    cin>>n;
    answer=fun(n);

    cout<<answer<<endl;

    return 0;
}

C++: #include<iostream>
using namespace std;
int main() {
	int n;
	int x;
	x = 1;
	cin >> n;
	for (int i = 0;i < n;i++)
	{
		x*(n - i);
	}
	cout << x <<endl;
	return 0;

}

C++: #include<iostream>
#include<cstdio>
#include<cstdlib> 
#include<iomanip>
#include<cmath>
#include<cstring>
#include<string>
#include<algorithm>

using namespace std;

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

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

using namespace std;


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

int main(){

	int n;
	cin>>n;
	cout<<fuc(n)<<endl;


	return 0;
}

C++: #include<stdio.h>
int main(void)
{
	int n,s,i;
	scanf("%d",&n);
	s=1;
	for(i=2;i<=n;i++){
		s=s*i;
	}
	printf("%d",s);
	return 0;
}