Program LastChance;

var n,p,k,x,m,r:longint;
    z:boolean;

    i,o:text;

begin
    assign(i,'fact.in');
    assign(o,'fact.out');
    reset(i);
    rewrite(o);
    Read(i,p);
    k:=0;n:=0; z:=true;
    While z and (k<=100000000) do begin
                                         inc(n);
                                         if (n div 5<>0) and (n mod 5 =0) then  begin
                                                                                 x:=n;m:=1;r:=0;
                                                                                 While (x<>m) do begin
                                                                                                   m:=m*5;
                                                                                                   r:=r+1;
                                                                                                   end;
                                                                                 k:=k+r;
                                                                                 end else;
                                         if (k=p) then z:=false
                                                  else z:=true;
                                   end;
     if (k=p) and (k<=100000000) then write(o,n)
                                 else write(o,-1);
    close(i);
    close(o);
end.