#include <stdio.h>
#include <climits>
using namespace std;

FILE *f,*g;

int main ()
{
    f=fopen("fact.in","r");
    g=fopen("fact.out","w");
    int nr5,nr,mij,ls,ld,gasit,p;
    fscanf(f,"%d",&p);
    ls=1;
    ld=INT_MAX;
    gasit=0;
    if (p==0) fprintf(g,"%d",1);
    else
    {
        while (ls<=ld && gasit==0)
        {
            mij=(ls+ld)/2;
            nr5=5;
            nr=0;
            while (nr5<=mij)
            {
                nr+=mij/nr5;
                nr5*=5;
            }
            if (nr==p)
            {
                mij-=mij%5;
                fprintf(g,"%d",mij);
                gasit=1;
                break;
            }
            else if (nr>p)
            {
                ld=mij-1;
            }
            else
            {
                ls=mij+1;
            }
        }
        if (ls>ld && gasit==0) fprintf(g,"%d",-1);
    }
    fclose(f);
    fclose(g);
    return 0;
}