#include <stdio.h>

int legendre(int n)
{
    int sum=0;
    int var=5;
    while(var<=n)
    {
        sum+=n/var;
        var=var*5;
    }
    return sum;
}

int p;
int min;

void cauta(int inf,int sup)
{
    if(inf>sup)
    {
        if(min==5*p+10)
            min=-1;
    }
    else
    {

        int mij=(sup+inf)/2;
        if(legendre(mij)<p)
            cauta(mij+1,sup);
        else
        {
            if(legendre(mij)==p)
                min=mij;
            cauta(inf,mij-1);
        }
    }
}

int main()
{
    freopen("fact.in","r",stdin);
    freopen("fact.out","w",stdout);
    scanf("%d",&p);
    min=5*p+10;
    if(p==0)
        printf("1");
    else
    {
        cauta(1,5*p);
        /*if(legendre(min)!=p)
            printf("-1");
        else*/
        printf("%d",min);
    }
    return 0;
}