4514 by rr

4*(5-1-4)=0
(-4+5)*1^4=1
-4+5+1^4=2
(4-5)*(1-4)=3
(-4+5)*1*4=4
(-4+5)*1+4=5
(-4+5)+1+4=6
(s(4)+5)*1^4=7
4+s((5-1)*4)=8
(4+5)*(-1+s(4))=9
s(4)*5*(-1+s(4))=10
4+5+s(1*4)=11
4+5-1+4=12
4+5*1+4=13
4+5+1+4=14
4*5-1-4=15
4*5-1*4=16
4*5-1-s(4)=17
4*5-s(1*4)=18
4*5-1^4=19
4*5*1^4=20