21=
2+3*4=
(2+3)*4=
30/3/5=
-250/50=
(10+2)*-(3-5)=
40-20-5=
4*(1/1-3/3+10/5-21/7+45/9-121/11+26/13-45/15+34/17-38/19+63/21-1/1+2002/1001)=