#include<fstream>
using namespace std;
int zero(int n)
{
    int s=0;
    long long numitor=5;
    while(numitor<=n)
    {
        s+=n/numitor;
        numitor*=5;
    }
    return s;
}
int main()
{
    ifstream cin("fact.in");
    ofstream cout("fact.out");
    int n,ans=0;
    cin>>n;
    int st=1,dr=(1LL<<31)-1;
    while(st<=dr)
    {
        int mij=(st+dr)/2;
        if(zero(mij)<n)
            st=mij+1;
        else
        {
            ans=mij;
            dr=mij-1;
        }

    }
    if(zero(ans)==n)
    cout<<ans;
    else
    cout<<-1;
    return 0;
}