#include<iostream>
#include<fstream>
#include<algorithm>

using namespace std;
ifstream fin("fact.in");
ofstream fout("fact.out");
int i,j,n,p,x,st,dr,mid;

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

int main()
{
    fin>>p;
    st=1;
    dr=80000010;
    while(st<=dr)
    {
        mid=(st+dr)/2;
        x=zero(mid);
        if(x>=p)
            dr=mid-1;
        else
            st=mid+1;
    }
    if(zero(st)==p)
        fout<<st;
    else
        fout<<-1;
    fin.close();
    fout.close();
    return 0;
}