#include <fstream>
#include <vector>
#define ll long long
using namespace std;
ifstream fin("fact.in");
ofstream fout("fact.out");
ll countZeros(ll val)
{
    ll r=0;
    for(int i=5;i<=val;i*=5)
        r+=val/i;
    return r;
}
ll nrOfZeros;
ll CB(ll st,ll dr)
{
    ll result=0;
    while(st<=dr)
    {
        ll m=(st+dr)/2;
        ll zeros = countZeros(m);
        if(zeros==nrOfZeros)
        {
            result=m;
            dr=m-1;
        }
        else
        {
            if(zeros>nrOfZeros)dr=m-1;
            else st=m+1;
        }
    }
    if(!result)return result;
    return -1;
}
void solve()
{
    fin>>nrOfZeros;
    if(nrOfZeros==0)
    {
        fout<<1;
        return;
    }
    fout<<CB(1,500000000);
}
int main()
{
    ios_base::sync_with_stdio(false);
    fin.tie(0);
    solve();
    return 0;
}