#include <stdio.h>
#include <string.h>
#include <math.h>
#include <stdlib.h>
#include <time.h>

FILE *in = fopen ("fact.in","r"), *out = fopen("fact.out","w");

int p;

long long nrz(long long n)
{
    long long s = 0;
    while (n)
    {
        s += n / 5;
        n = n / 5;
    }

    return s;
}

void find()
{
    long long st = 1, dr = 1000000000000000000LL;

    while (st < dr)
    {
        long long m = st + (dr - st) / 2;

        if (nrz(m) < p)
            st = m + 1;
        else
            dr = m;
    }

    if (nrz(st) != p)
        fprintf(out, "-1");
    else
        fprintf(out, "%lld", st);
}

int main()
{
    fscanf(in, "%d", &p);
    find();

    return 0;
}