#include <stdio.h>
#include <climits>
int nr0f(int n)
{
    int p5=5,s=0;
    while(n>=p5)
    {
        s+=n/p5;
        p5*=5;
    }
    return s;
}

int main()
{
    int li=1,lf=INT_MAX-1,p,m,n0;
    scanf("%d",&p);
    while(li<=lf)
    {
        m=(li+lf)/2;
        n0=nr0f(m);
        if(n0>=p) lf=m-1;
        else li=m+1;
    }
        if(nr0f(li)==p) printf("%d",li);
        else printf("-1");
    return 0;
}