#include <iostream>
#include <fstream>

using namespace std;

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

int v[100001],n;

bool ok(int val,int target)
{
    long long p5=5,cnt=0;
    while(p5<=val)
    {
        cnt+=val/p5;
        p5*=5;
    }
    return (cnt>=target);
}

int f(int val)
{
    long long st=1,dr=1e8*5,mid,rasp;
    while(st<=dr)
    {
        mid=(st+dr)/2;
        if(ok(mid,val))
        {
            rasp=mid;
            dr=mid-1;
        }
        else st=mid+1;
    }
    return rasp;
}

int main()
{
    int p;
    fin>>p;
    fout<<f(p);
    return 0;
}