#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 last,first,mid;
    f>>P;
    first = 1; last = 6*P;

    while (first<=last) {
        mid = first + (last-first)/2;
        if (zero(mid)>=P)
            last = mid - 1;
        else
            first = mid + 1;

    }
    if(zero(first)==P)
        g<<first;
    else
        g<<"-1";

}