#include<iostream>
#include<fstream>
#include<algorithm>
using namespace std;
ifstream f("fact.in");
ofstream g("fact.out");
int zero(int x)
{
    int p5 = 5;
    int d = 0;
    while (x/p5 != 0) {
        d =d+ (x/p5);
        p5=p5*5;
    }
    return d;
}
int P;
int main()
{
    int N=0,P,i=1;
    f>>P;
    for(i=0; ; i++)
    {
        if(zero(i)==P)
        {
            N=i;
            break;
        }
        if(zero(i)>P)
        {
            N=-1;
            break;
        }
    }
    g<<N;

}