#include <fstream>
using namespace std;
ifstream fin("fact.in");
ofstream fout("fact.out");
long long n,p,i,j,nr,mijl,ok,k;
int nr0(int x)
{
    int s=0, p=5;
    while(p<=x)
    {
        s=s+x/p;
        p=p*5;
    }
    return s;
}
int main()
{
    fin>>p;
    if(p==0) {fout<<1; return 0;}
    if(p==5) {fout<<-1; return 0;}
    if(p==1) {fout<<5; return 0;}
    i=0;
    j=2000000000;
    ok=0;
    while(i<=j)
    {
        mijl=(i+j)/2;
        k=nr0(mijl);
        if(k<p) i=mijl+1;
        else j=mijl-1;
    if(k==p) {ok=mijl;}

    }
    if(ok==0) {fout<<-1; return 0;}
    if(i==0) {fout<<1; return 0;}
    else {fout<<ok; return 0;}
    return 0;
}