#include <stdio.h>

using namespace std;

int find_5pow(int n)
{
    if (n == 0) {
        return 1;
    }

    int nr = 0;
    while (n % 5 == 0) {
        nr++;
        n /= 5;
    }
    return nr;
}

int main()
{
    FILE *file_in = fopen("fact.in", "r");
    FILE *file_out = fopen("fact.out", "w");
    int p, n = 0, nr = 0;
    fscanf(file_in, "%d", &p);
    if (p == 0) {
        fprintf(file_out, "1");
        return 0;
    }

    while (nr < p) {
        nr += find_5pow(n);
        n += 5;
    }
    fprintf(file_out, "%d\n", n);
}