#include <stdio.h>
#include <stdlib.h>
#include <limits.h>

int count(int n) // nr de zerouri dat de cate ori putem imparti factorialul la 5
{
    int nr = 0;
    while (n >= 5)
    {
        nr += n / 5;
        n /= 5;
    }
    return nr;
}

int find(int p)
{
    int st = 1, dr = p * 5;
    while (st < dr)
    {
        int mij = (st + dr) / 2;
        int zero = count(mij);
        if (zero < p)
            st = mij + 1;
        else
            dr = mij;
    }
    return st;
}

int main()
{
    FILE *pf = fopen("fact.in", "r");
    FILE *pg = fopen("fact.out", "w");

    int p;
    fscanf(pf, "%d", &p);

    int x = find(p);
    fprintf(pg, "%d", x);

    fclose(pf);
    fclose(pg);
    return 0;
}