C :

#include <stdio.h>
#include <stdlib.h>
int main()
{
	
	int n;	
    long long a[50]={0},i;
    scanf("%d",&n);
    a[1]=1;
    for(i=2;i<=49;i++)
        a[i]=a[i-1]*i;
    printf("%lld",a[n]);
	return 0;
}

C++ :

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

Pascal :

program nnnn(input,output);
var
    n:int64;
function get(x:int64):int64;
begin
    if x=0 then
        exit(1);
    exit(get(x-1)*x);
end;
begin
    readln(n);
    if n<0 then
    	writeln(1)
    else
    	writeln(get(n));
end.

Python :

# coding=utf-8
n=int(input())
s=1
for i in range(1,n+1):
    s=s*i
print(s)