#include <iostream>
#include<fstream>
using namespace std;

int p;


    ifstream f("fact.in");
    ofstream g("fact.out");
int fun(long long x)
{
    long long c=5,nr=0;
    while(x/c!=0)
    {
        nr=nr+x/c;
        c=c*5;
    }
    return nr;
}

void binary(long long st,long long dr)
{
    long long med;
    med=(st+dr)/2;
    if(fun(med)==p&&med%5==0)
        g<<med<<endl;


    else
        if(fun(med)>p)
            binary(st,med-1);
        else
            binary(med+1,dr);

}
int main()
{


    long long n;
    f>>p;
    if(p==0)
        g<<1<<endl;
    else
    binary(1,100000000);
    return 0;
}