lcm and gcd using prime factorization, Fortran

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program hello
implicit none
integer::num,num1
call primefact(num,num1)
end program

subroutine primefact(num,num1)
implicit none
integer,parameter::n=100
integer::i,num,num1,c=0,c1=0,gcd=1,lcm=1,j
integer,dimension(n)::A,B
read(*,*)num
if(num<=1)then
print'(3x,A50)','Program will not work since 1 has only one factor 1 itself.'
end if
write(*,16)'Prime factors of 24 are :'
16 format(4x,A30)
do i=2,num
do while(mod(num,i)==0)
!write(*,10)i
c=c+1;
A(c)=i;
!10 format(35x,I2)
num=num/i;
end do
end do
write(*,*)(A(i),i=1,c)
read(*,*)num1
if(num1<=1)then
print'(3x,A50)','Program will not work since 1 has only one factor 1 itself.'
end if
write(*,17)'Prime factors of 32 are :'
17 format(4x,A30)
do i=2,num1
do while(mod(num1,i)==0)
!write(*,11)i
c1=c1+1;
B(c1)=i;
!11 format(35x,I2)
num1=num1/i;
end do
end do
write(*,*)(B(i),i=1,c1)
do i=1,c
if(A(i)==B(i))then
gcd=gcd*A(i);
end if
end do
write(*,20)'Gcd of 24 and 32 is :',gcd
20 format(1x,A30,2x,I4)
do i=1,c
!do j=1,i
if (A(i)==B(i))then
lcm=lcm*A(i)
else
lcm=lcm*A(i)*B(i)
end if 
end do
do i=c+1,c1
lcm=lcm*B(i);
end do
write(*,22)'lcm of 24 and 32 is :',lcm
22 format(1x,A30,2x,I4)
end subroutine

Show compiler warnings [ - ] Show input
Compilation time: 0.59 sec, absolute running time: 0.16 sec, cpu time: 0.01 sec, memory peak: 5 Mb, absolute service time: 0,83 sec