Program P1;
var n,m,s,nr : longint;
    fi,fo : text;

begin assign(fi,'fact.in'); reset(fi); readln(fi,nr); close(fi);
      assign(fo,'fact.out'); rewrite(fo);
      if nr<2 then write(fo,'1') else begin
                                       s:=0;
                                       n:=2*nr+2;
                                             if  nr>=10 then n:=4*nr
                                                          else if nr>=4 then  n:=4*n+1;
      while s<>nr  do begin
                      m:=5;
                      s:=0;
                      n:=n+1;
                      while m<=n do begin
                                       s:=s+(n div m);
                                       m:=5*m
                                       end;
                      end;
                      write(fo,n);
                      end;

      close(fo);
end.