Yes, I have to use restart and also delete all the prior results. Thanks for your help.

I´m using Maple 10 Classic and this is all the procedure: > eucex:=proc(a::integer,b::integer) > local x0,x1,y0,y1,r0,r1,x,y,r; > x0:=1: x1:=0: y0:=0: y1:=1: r0:=a: r1:=b: x:=0: y:=1: r:=r1: > while irem(r0,r1,'q')<>0 do > x1:=x0-q*x1: x0:=x: x:=x1: > y1:=y0-q*y1: y0:=y: y:=y1: > r:=irem(r0,r1): r0:=r1: r1:=r: > od: > [r,x,y]; > end: > EJEMPLO > a:=8; a := 8 > b:=13; b := 13 > eucex(a,b); eucex(8, b)