#include<stdio.h>
int zero(int n)
{
    int nr=0;
    while(n>=5)
    {
        nr+=n/5;
        n/=5;
    }
    return nr;
}
int caut(int x)
{
    int i=0,pas=1<<30;
    while(pas!=0)
    {
        if(zero(i+pas)<x)
            i+=pas;
        pas/=2;
    }
    return i+1;
}
int main()
{
    int p,n;
    freopen("fact.in","r",stdin);
    freopen("fact.out","w",stdout);
    scanf("%d",&p);
    n=caut(p);
    if(zero(n)==p)
        printf("%d",n);
    else
        printf("-1");
    return 0;
}