#include <fstream>

using namespace std;

ifstream fin("fact.in");
ofstream fout("fact.out");

long long p,bot=1,top=1000000000,mid,z;

int nrnada(int h)
{int nr=0;
while(h>=5)
{
   nr+=(h/=5);
}
    return nr;
}

int main()
{
fin>>p;
if(!p)fout<<1;
else{while(bot<=top)
{
    mid=(bot+top)/2;
    z=nrnada(mid);
    if(z>=p)top=mid-1;
    else bot=mid+1;

}
if(nrnada(bot)==p)fout<<bot;
else fout<<-1;
}

    return 0;
}