#include <cstdio>
using namespace std;
int p,tmp;
int main()
{
    freopen("fact.in", "r", stdin);
    freopen("fact.out", "w", stdout);
    scanf("%i", &p);
    int zero = 0;
    int num=0;
    while(zero<p)
    {
        num++;
        tmp = num;
        while(tmp%5 == 0)
        {
            tmp/=5;
            zero++;
        }
    }
    printf("%i\n", num);
    return 0;
}