#include<fstream>   
using namespace std;   
int main()   
{      
    long p,i,x=0;   
    ifstream in("fact.in");   
    ofstream out("fact.out");   
    in>>p;   
    while (p/35!=0)   
    {x=x+125;   
    i=x;   
    p=p-28;   
    while (i%5==0)   
    {i=i/5;   
    p--;}}   
    while (p/5!=0)
	{x=x+25;
	i=x;
	p=p-4;
	while (i%5==0)
	{i=i/5;
	p--;}}
	x=x+p*5;
	out<<x;
    in.close();   
    out.close();   
    return 0;   
}