#include <fstream>
using namespace std;
ifstream fi("fact.in");
ofstream fo("fact.out");
long long sol,n;

long long numar(long long x)
{
    long long s=0;
    for(long long p=5;x/p;p*=5) s+=x/p;
    return s;
}

long long caut_bin(long long p,long long u,long long x)
{
    long long m;
    while(p<u)
    { m=(p+u)/2;
    if(numar(m)<x) p=m+1;
    if(numar(m)>=x)u=m;
    }
m=(p+u)/2;
if(numar(m) < x) m++;
return m;
}

int main()
{

fi>>n;
sol=caut_bin(1,numar(100000000000),n);
if(numar(sol) == n ) fo<<sol;
                else fo<<"-1";




    return 0;
}