#include <fstream>
#include <cmath>
 
using namespace std;
 
long n, m;
 
int suma(int j, int k);
int fact(long p);
 
int main(int argc, char* argv[])
{
    long p;
    int i;
 
    ifstream inFILE("fact.in");
    ofstream outFILE("fact.out");
 
    inFILE >> p;
    outFILE << fact(p);
 
    return 0;
}
 
int suma(int j, int k)
{
    long s = 0;
 
    for (int i = 1; i <= k; i++)
    {
        s = s + floor(j / pow(5,(double)i));
    }
 
    return s;
}
 
int fact(long p)
{
    int i;
    long a, b, j;
 
    if (p == 0)
        return 1;
    else
    {
        m = 1;
 
        for(i = 1; m <= p;i++)
            m = m + pow(5,(double)i);
 
        if(p == m-1)
            return -1;
        else
            m = m - pow(5,(double)--i);
 
        a = ceil(p * pow(5,(double)i) / m);
        b = floor((p + i) * pow(5,(double)i) / m);
 
        for(j = a; j < b; j++)
        {
            if (suma(j,i) == p)
                return j;
        }
 
        return -1;
     
    }
 
}