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++: #define _USE_MATH_DEFINES
#include<iostream>
#include<string>
#include<queue>
#include<cmath>
#include<map>
#include<set>
#include<list>
#include<iomanip>
#include<vector>
#include<random>
#include<functional>
#include<algorithm>
#include<stack>
#include<cstdio>
#include<bitset>
#include<unordered_map>
#include<climits>
#include<fstream>
using namespace std;
///////////////////library zone!!!!!!!!!!!!!!!!!!!!!!!!!!!!
typedef long long ll;
typedef long double ld;
#define all(a) (a).begin(),(a).end()
#define EPS (1e-5)
const ll Mod = 1000000007;
const ll mod = 998244353;
struct H {
	ll x, y;
	bool operator<(const H &b) const {
		if (x != b.x) return x < b.x;
		return y < b.y;
	}
	bool operator>(const H &b) const {
		if (x != b.x) return x > b.x;
		return y > b.y;
	}
	bool operator==(const H &b) const { return x == b.x&&y == b.y; }
	bool operator!=(const H &b) const { return (*this) != b; }
};
struct P {
	ll pos, cost;
	bool operator<(const P &b) const { return cost < b.cost; }
	bool operator>(const P &b) const { return cost > b.cost; }
};
struct B {
	ll to, cost;
};
struct E {
	ll from, to, cost;
	bool operator<(const E &b) const { return cost < b.cost; }
	bool operator>(const E &b) const { return cost > b.cost; }
};
template<typename T, typename U>
void chmin(T &a, U b) {
	if (a > b) a = b;
}
template<typename T, typename U>
void chmax(T &a, U b) {
	if (a < b) a = b;
}
template<typename T>
T max_0(T a) {
	if (a < 0) return 0;
	return a;
}
template<typename T>
T min_0(T a) {
	if (a > 0) return 0;
	return a;
}
ll read() {
	ll u;
	ll k = scanf("%lld", &u);
	return u;
}
ll gcd(ll i, ll j) {
	if (i > j) swap(i, j);
	if (i == 0) return j;
	return gcd(j%i, i);
}
ll mod_pow(ll x, ll n, ll p) {
	ll res = 1;
	while (n > 0) {
		if (n & 1) res = res * x % p;
		x = x * x % p;
		n >>= 1;
	}
	return res;
}//x^n%p
vector<string>split(string s, char c = ' ') {
	vector<string>vec;
	string h = "";
	for (int i = 0; i < s.size();) {
		int j = i;
		while (j < s.size() && s[j] != ' ') {
			h += s[j++];
		}
		if (h.size() > 0) vec.push_back(h);
		h = "";
		i = j + 1;
	}
	return vec;
}
const ll Inf = 3023372036854775807;
const int inf = 1500000000;
#define int long long
//----------------------------------------------------
class Vec2 {
public:
	ld x, y;
	Vec2() { x = 0, y = 0; }
	Vec2(ld x, ld y) :x(x), y(y) {}
	ld length() {
		return sqrt(x*x + y * y);
	}
	void normal() {
		ld len = this->length();
		if (len == 0) return;
		x /= len, y /= len;
	}
	Vec2 operator+(Vec2 vec) {
		return Vec2(x + vec.x, y + vec.y);
	}
	Vec2 operator-(Vec2 vec) {
		return Vec2(x - vec.x, y - vec.y);
	}
	Vec2 operator*(int cons) {
		return Vec2(x*cons, y*cons);
	}
	ld operator*(Vec2 vec) {
		return x * vec.x + y * vec.y;
	}
	ld operator%(Vec2 vec) {
		return x * vec.y - y * vec.x;
	}
};
ld dot(Vec2 a, Vec2 b) {
	return a.x*b.x + a.y*b.y;
}
ld cross(Vec2 a, Vec2 b) {
	return a.x*b.y - a.y*b.x;
}
ld areaIntegral(Vec2 a, Vec2 b) {
	return abs(a.x*b.y - a.y*b.x) / 2.0;
}
class Vec3 {
public:
	ld x, y, z;
	Vec3() { x = 0, y = 0, z = 0; }
	Vec3(ld x, ld y, ld z) :x(x), y(y), z(z) {}
	ld length() {
		return sqrt(x*x + y * y + z * z);
	}
	void normal() {
		ld len = this->length();
		if (len == 0) return;
		x /= len, y /= len, z /= len;
	}
	Vec3 operator+(Vec3 vec) {
		return Vec3(x + vec.x, y + vec.y, z + vec.z);
	}
	Vec3 operator-(Vec3 vec) {
		return Vec3(x - vec.x, y - vec.y, z - vec.z);
	}
	Vec3 operator*(int cons) {
		return Vec3(x*cons, y*cons, z*cons);
	}
	ld operator*(Vec3 vec) {
		return x * vec.x + y * vec.y + z * vec.z;
	}
};
ld dot(Vec3 a, Vec3 b) {
	return a.x*b.x + a.y*b.y + a.z*b.z;
}
class Line {
public:
	Vec2 from, to;
	Line(Vec2 from, Vec2 to) :from(from), to(to) {}
};
Line getPerpendicularBisector(Line line) {
	int cx = (line.from.x + line.to.x) / 2, cy = (line.from.y + line.to.y) / 2;
	Vec2 p = Vec2(cx + (line.from.y - line.to.y), cy + (line.to.x - line.from.x));
	return Line(Vec2(cx, cy), p);
}
signed main() {
	int n, sum = 1;
	n = read() + 1;
	while (--n) {
		sum *= n;
	}
	cout << sum << endl;
}

C++: #include <iostream>

using namespace std;

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

	cin >> n;
	for (int i = 1; i <= n; i++) {
		if (n == 0) {
			ans = 1;
			break;
		}
		else {
		ans *= i;
		}
	}
	cout << ans << endl;
}

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

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

C++: #include <iostream>

using namespace std;

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

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

    return 0;
}

C++: #include<stdio.h>

int kaijo(int);


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

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

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

C++: #include <iostream>

using namespace std;

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

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

C++: #include <iostream>

using namespace std;

int main() {
    long long answer = 1;
    int n;
    cin >> n;

    for (int i = n; i != 0; i--) {
            answer *= i;
    }
cout << answer << endl;
return 0;
}

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

long factorial(int n)
{
	if (n==1) return 1;
	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 main() {
  long long n, res = 1;
  cin >> n;
  for (int i = 1; i <= n; ++i) res *= i;
  cout << res << endl;
}

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

int Kaijo(int n) {
	int m;
	if (n == 0)
		return 1;
	m = Kaijo(n - 1);
	return m*n;
}

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

C++: #include <stdio.h>

int main(void) {
	int n, flg=0;
	int fact[20];
	char buf[256];
		
	for (int i=0; i<20; i++)  fact[i]=0;
	fact[0]=1;
	
	fgets(buf, sizeof(buf), stdin);
	sscanf(buf, "%d", &n);
	
	if (n<1 || n>20) return 1;
	
	
	for (int i=2; i<=n; i++) {
		for (int j=19; j>=0; j--) {
			fact[j] *= i;
			for (int k=0; k<20; k++) {
				if (fact[k]/10 >= 1) {
					fact[k+1] += fact[k]/10;
					fact[k] = fact[k]%10;
				}
			}
		}
	}
	
	for (int i=19; i>=0; i--) {
		if (flg==0 && fact[i]==0)  continue;
		flg=1;
		printf("%d", fact[i]);
	}
	
	printf("\n");
	
	return 0;
}

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

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

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

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

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