function z=shubert(x,y)          %Shubert函數
z=((1*cos((1+1)*x+1))+(2*cos((2+1)*x+2))+(3*cos((3+1)*x+3))+(4*cos((4+1)*x+4))+(5*cos((5+1)*x+5))).*((1*cos((1+1)*y+1))+(2*cos((2+1)*y+2))+(3*cos((3+1)*y+3))+(4*cos((4+1)*y+4))+(5*cos((5+1)*y+5)));