#include <fstream>

using namespace std;

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

int zero (int n)
{
    int sol=0;
    while (n>0)
    {
        sol+=n/5;
        n/=5;
    }
    return sol;
}

int main()
{
    int p,n2=1;
    ci >> p;
    while (n2*2<=5*p)
    {
        n2*=2;
    }
    int sol=5*p+1;
    for (int step=n2; step>0; step/=2)
    {
        if (sol-step>0 && zero(sol-step)>=p)
        {
            sol-=step;
        }
    }
    if (zero(sol)>p)
    {
        co << "-1";
    }
    else
    {
        co << sol;
    }
    return 0;
}