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

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