#include <iostream>
#include <fstream>

using namespace std;

ifstream in("fact.in");
ofstream out("fact.out");

int p;

int nrDe0(int n)
{
    int sum=0;
    int exp=5;
    while (n>=exp) {
        sum+=(n / exp);
        exp*=5;
    }
    return sum;
}

void cautBin()
{
    int m,s=0,d=1000000000;
    while(s<=d)
    {
        m=(s+d)/2;
        if(nrDe0(m)<p)s=m+1;
        else d=m-1;
    }
    if(nrDe0(s)!=p)
        out<<-1;
    else
        out<<s;
}

int main()
{
    in>>p;
    if(p==0)
        out<<1;
    else
        cautBin();
    return 0;
}