#include<fstream>
using namespace std;
int zero(int n)
{
    int x=0,p=5;
    while(n/p!=0)
    {x+=n/p;p*=5;}
    return x;
}

int caut(int n)
{
    int min=0, max=999999999,m,t;
    while(min<=max)
    {
    m=min+(max-min)/2;
    t=zero(m);
    if(t==n) return m-m%5;
    if(t>n) max=m-1;
    else min=m+1;
    }
    return -1;
}

int main()
{
    int n,x;
    ifstream fin("fact.in");
    ofstream fout("fact.out");
    fin>>n;
    if(n==0) fout<<1;
    else fout<<caut(n);
    fin.close(), fout.close();
}