#include <iostream>
#include <cstdio>
#include <climits>
#include <fstream>
using namespace std;
int li,lf,m,p;
int nr0f(int n)
{
    int p5=5,s=0;
    while(n>=p5)
    {
        s+=n/p5;
        p5*=5;
    }
    return s;
}
int main()
{
    FILE *f = fopen("fact.in", "r");
    FILE *g = ("fact.out", "w");
    li=1;lf=INT_MAX-1;
    fscanf (f "%d", &p);
    li=1;lf=INT_MAX;
   while(li<=lf)
   {
       m=(li+lf)/2;

       if(nr0f(m)>=p)
        lf=m-1;
       else
        li=m+1;
   }
   if(nr0f(li)==p)
        fprintf(f "%d", li);
   else
        fprintf(f "-1");
    return 0;
}