#include <iostream>
#include <fstream>

using namespace std;

ifstream in("fact.in");
ofstream out("fact.out");

const long int PMAX = 1000000000;
const int pw2=536870912;
int nrzero(int n)
{
    long int five=5,result=0;
    while(n>=five)
    {
        result=result+n/five;
        five=five*5;
    }
    return result;
}

int CBclasic(int x)
{
    int sol=PMAX;
    for(int i=pw2;i>=1;i=i/2)
    {
        if(sol-i>=1 && nrzero(sol-i)>=x)
            sol-=i;
    }
    return sol;
}

int main()
{
    long long int x;
    in>>x;
    out<<CBclasic(x);


}