#include <fstream>
#define ll long long
using namespace std;
ifstream fin("fact.in");
ofstream fout("fact.out");
ll nrz(ll x)
{
    int k=0;
    ll c=5;
    while(c<=x)
    {
        k+=x/c;
        c*=5;
    }
    return k;
}
int main()
{
    ll n;
    fin >> n;
    ll k=n;
    while(nrz(5*k)!=n)
    {
        k+=(n-nrz(5*k));
    }
    fout << 5*k;
}