! NAME: T.S.Vilasini
! ROLL NUMBER: I14PH010
! DATE OF PROGRAM:
program Lagrange
integer::n,o,m
real::a1,a2,a3,a4,a5,p,c,d,b,e,f,a
dimension x(50),y(50),t1(50),t2(50),t3(50),t4(50),t5(50),temp(5)

12 write(*,*),'number of x points'
read(*,*),n

write(*,*),'number of y points'
read(*,*),o

write(*,*),'values of x'
do i=1,n
    read(*,*),x(i)
enddo

write(*,*),'values of y'
do i=1,o
    read(*,*),y(i)
enddo

write(*,*)'Select 1 if there is a third variable'
read(*,*),d

if (d==1) then
    goto 3
else
    goto 7
endif

3 write(*,*),'values of t1,t2,t3,t4,t5'
do i=1,n
    read(*,*)t1(i),t2(i),t3(i),t4(i),t5(i)
enddo

1 write(*,*),'x at which calculation is to be done'
read(*,*),x0
a=0
do i = 1,n
    p = 1
    do j = 1,n
    if(i.NE.j)then
        p = p*(x0-x(j))/(x(i)-x(j))
    endif
    enddo
    if(d==1)then
        temp(1) = temp(1)+p*t1(i)
        temp(2) = temp(2)+p*t2(i)
        temp(3) = temp(3)+p*t3(i)
        temp(4) = temp(4)+p*t4(i)
        temp(5) = temp(5)+p*t5(i)
    else
        a = a+p*y(i)

    endif
enddo

if(d.NE.1)then
write(*,*)'value at x =',x0,'is',a
goto 11
endif

14 write(*,*),'y at which calculation is to be done'
read(*,*),y0
a1=0
a=0

do i =1,o
    p = 1
    do j = 1,o
    if(i.NE.j)then
        p = p*(y0-y(j))/(y(i)-y(j))
    endif
    enddo
    if(d==1)then
        a1 = a1+p*temp(i)
    else
        a = a+p*x(i)
    endif
enddo

if(d==1)then
        write(*,*),'value at x =',x0,'y =',y0,'is',a1
    else
        write(*,*),'value at y =',y0,'is',a
    endif

11 write(*,*),'select 1 if further calculations is to be done'
read(*,*),c

if (c==1) then
    write(*,*),'reset the values of x and y. If yes then select 1.If not select 0'
    read(*,*),f
    if (f==1) then
        goto 12
    else
        goto 7
    endif
else
    goto 2
endif

7 write(*,*),'select 1 if calculating x else 0 if calculating y'
read(*,*),b
if (b==1) then
    goto 1
else
    goto 14
endif

goto 11

2 end program