#include<fstream>
using namespace std;
int zerouri(int x)
{
    int ans=0;
    while(x>=5)
    {
        ans=ans+x/5;
        x=x/5;
    }
    return ans;
}
int cautarebinara(int p)
{
    int st=1,dr=p*5,mij;
    if(p==0)
        return 1;
        while(st<dr)
        {
            mij=(st+dr)/2;
        if(zerouri(mij)==p)
            return mij-mij%5;
        if(zerouri(mij)>=p)
            dr=mij-1;
        else
            st=mij+1;
        }
    return -1;
}
int main()
{
    ifstream cin("fact.in");
    ofstream cout("fact.out");
    int p;
    cin>>p;
    cout<<cautarebinara(p);
}
//daca am 13 si am nev de 2 zeriouri le am in 5*2 si 10 atunci il reduc la 13