#include <stdio.h>
#include <algorithm>
using namespace std;

int p;

int check(long long n)
{
    int i,n5=0,aux=0;
    for(i=1;i<=n;i++)
    {
        if(i%5==0){
            aux = i;
            while(i%5==0)
            {
                n5++;
                i/=5;
            }
            i = aux;
        }
    }
    return n5;
}

int main()
{
    freopen("fact.in","r",stdin);
    freopen("fact.out","w",stdout);
    scanf("%d",&p);
    long long pas = 1 << 20;
    int k;
    for(k =0; pas ;pas>>=1)
    {
        if(check(k+pas) < p)
            k+=pas;
    }
    printf("%d\n", k+1);


    fclose(stdin);
    fclose(stdout);
}