var a:array[1..12] of int64;  N:longint; P:int64; i:byte; F:text;
 function CheckZero(N:longint):int64;
  var r:int64;
   begin
    i:=1;
     r:=0;
     while a[i]<N do
      begin
      r:=r+N div a[i];
      inc(i);
     end;
    CheckZero:=r;
  end;
Begin
a[1]:=5;
N:=10;
assign(F, 'fact.in');
reset(F);
readln(F, P);
close(F);
 for i:=2 to 12 do
 a[i]:=a[i-1]*5;
while CheckZero(N)<P do
 N:=N+5*((P-CheckZero(N)) div 2);
 assign(F, 'fact.out');
 rewrite(F);
 if CheckZero(N)<>P then N:=-1;
 writeln(F, N);
close(F);
end.