2000-1997+1994-1991+1998-1995+1982-1979+...+14-11+8-5+2
=(2000-1997)+(1994-1991)+(1998-1995)+(1982-1979)+...+(14-11)+(8-5)+2
=3*666/2+2
=1001
2000-1997+1994-1991+1998-1995+1982-1979+...+14-11+8-5+2
=(2000-1997)+(1994-1991)+(1998-1995)+(1982-1979)+...+(14-11)+(8-5)+2
=3*666/2+2
=1001