#include <stdio.h>

using namespace std;

int zero(int n)
{
    int nrz=0;
    while(n>=5)
    {
        nrz+=n/5;
        n/=5;
    }
    return nrz;
}

int main()
{
    int p,pas,i=0;
    freopen("fact.in","r",stdin);
    freopen("fact.out","w",stdout);
    pas=1>>30;
    scanf("%d",p);
    while(pas!=0)
    {
        if(zero(i+pas)<p)
            i+=pas;
        pas/=2;
    }
    if(zero(i+1)==p)
        printf("%d",i+1);
    else printf("-1");
    return 0;
}