#include <fstream>

using namespace std;
ifstream in("fact.in");
ofstream out("fact.out");
int p;
int des(int n)
{
    int x=0;
    for(; n; x += n / 5 ,n/=5);
        return x;
}
int main()
{
    in>>p;
    int st=1,dr =5*p,m,r=1;
    while(st<=dr)
    {
        m=(st +dr)/2;
        if(des(m)>=p)
            r=m,dr=m-1;
        else
            st=m+1;
    }
    if(des(r)==p)
        out<<r;
    else
        out<<"-1";
    return 0;
}