Program P1;
var n,m,s,nr : qword;
    fi,fo : text;
begin
      assign(fi,'fact.in'); reset(fi); readln(fi,nr); close(fi);
      s:=0; n:=0;
      while s<>nr do begin
      m:=5; s:=0; n:=n+1;
      while m<=n do begin
                    s:=s+ (n div m) ;
                    m:=m*5;
                    end;
                    end;
      assign(fo,'fact.out'); rewrite(fo);
      if nr=0 then writeln(fo,'1')
              else writeln(fo,n);  close(fo);
end.