Program SIMPSON_5VAR
        IMPLICIT DOUBLE PRECISION (A-H,O-Z)

        call cpu_time(start)
        a=0d0
        b=1d0
        c=(a+b)/2d0
        r=(b-a)/6d0*(g5(a)+4d0*g5(c)+g5(b))

        open(20,File="ejerc10simp5var.xls")

        write(20,*)r
        call cpu_time(finish)
        write(20,*)"Temps = ",finish-start ,"s"
        close(20)
        END


        FUNCTION  g1(x1,x2,x3,x4,x5)
        Implicit Double Precision (A-H,O-Z)

         g1=exp(-x1**2-x2**2-x3**2-x4**2-x5**2)*cos(x2*x1+x3*x2+
     &   x3*x4+x4*x5+x5*x1)
        END

        Function g2(x2,x3,x4,x5)
        IMPLICIT DOUBLE PRECISION (A-H,O-Z)
        a=0d0
        b=1d0
        c=(a+b)/2d0
        g2=(b-a)/6d0*(g1(a,x2,x3,x4,x5)+4d0*g1(c,x2,x3,x4,x5)+
     &  g1(b,x2,x3,x4,x5))
        END


        Function g3(x3,x4,x5)
        IMPLICIT DOUBLE PRECISION (A-H,O-Z)
        a=0d0
        b=1d0
        c=(a+b)/2d0
        g3=(b-a)/6d0*(g2(a,x3,x4,x5)+4d0*g2(c,x3,x4,x5)+g2(b,x3,x4,x5))
        END
        
        Function g4(x4,x5)
        IMPLICIT DOUBLE PRECISION (A-H,O-Z)

        a=0d0
        b=1d0
        c=(a+b)/2d0
        g4=(b-a)/6d0*(g3(a,x4,x5)+4d0*g3(c,x4,x5)+g3(b,x4,x5))
        END
        
        Function g5(x5)
        IMPLICIT DOUBLE PRECISION (A-H,O-Z)

        a=0d0
        b=1d0
        c=(a+b)/2d0
        g5=(b-a)/6d0*(g4(a,x5)+4d0*g4(c,x5)+g4(b,x5))
        END