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

int main()
{
    freopen("fact.in","r",stdin);
    freopen("fact.out","w",stdout);
    int n,i,nr5=0,aux;
    scanf("%d",&n);
    i=0;
    while(nr5<n)
    {
        ++i;
        if(i%5==0)
        {
            aux=i;
            while(aux%5==0)
            {
                aux=aux/5;
                nr5++;
            }
        }
    }
    printf("%d",i);
    return 0;
}