#include <stdio.h>
#include <stdlib.h>
long long n;
int main()
{
    FILE *f,*g;
    f=fopen("fact.in","r");
    g=fopen("fact.out","w");
    int p,ok,nr,p1,i;
    fscanf(f,"%d",&p);
    if(p==0)
    fprintf(g,"%d\n",1);
    else
    {
        p1=5;
        n=5;
        nr=1;
        while(nr<p)
        {
            nr=0;
            for(i=5;i<=p1;i*=5)
            {
            nr+=(n/i);
            }
            if(nr<p)
            n+=5;
            if(n==p1*5)
            p1*=5;
        }
        if(nr>p)
        fprintf(g,"%d\n",-1);
        else
        fprintf(g,"%d\n",n);
    }
    return 0;
}