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

int p;


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

int binary(long long st,long long dr)
{
   while(st<=dr)
    {
        long med=(st+dr)/2;

       long x=fun(med);
        if(x==p && med%5==0)
        {
            return med;
        }
        else
        {
            if(x<p)
                st=med+1;
            else
                dr=med-1;
        }
    }
    return -1;
}

int main()
{


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