#include <iostream>
#include <fstream>
using namespace std;
unsigned long n,p;

unsigned long numar_zerouri (unsigned long x)
{
    unsigned long zero=0;
    while (x/5>0)
    {
        zero+=x/5;
        x/=5;
    }
    return zero;
}

long cautare (unsigned long left, unsigned long right)
{
    if (right==left) return right;
    else
    {
    unsigned long mijloc=(left+right)/2, zerouri=numar_zerouri(mijloc);
   // printf("%d<>%d %d: %d=?%d\n", left,right,mijloc, zerouri, p);
    if (zerouri>=p) cautare (left, mijloc-1);
    else if (zerouri<=p) cautare (mijloc+1, right);
    }
}

int main()
{
    freopen("factorial.in", "r", stdin);
    freopen("factorial.out", "w", stdout);
    scanf("%d", &p);
    printf("%d", cautare(1, 80000));
    return 0;
}