#include <fstream>

#include<algorithm>

using namespace std;

int zerouri (int n)
{
    int rez=0;
    while(n>=5)
    {
        rez+=n/5;
        n=n/5;
    }
    return rez;
}

int caut (int p)
{
    int i=0,pas=1<<30;
    while(pas!=0)
    {
        if(zerouri(i+pas)<p)
            i+=pas;
        pas/=2;
    }
    return 1+i;
}

int main()
{
    int p, n;
    ifstream f("fact.in");
    ofstream g("fact.out");
    f>>p;
    n = caut(p);
    if(zerouri(n) != p)
        g<<"-1";
    else
        g<<n;
    return 0;
}