Error in Report Execution

Hi

I am getting an Error as '"ALPHA" and "IT-F2" are type-incompatible.'

Can anyone solve it.

Report abc.

data: begin of it occurs 5,

f1 like sy-index,

f2,

end of it,

alpha(5) value 'ABCDE'.

do 5 times varying it-f2 from alpha0 next alpha1.

it-f1 = sy-index.

append it.

enddo.

it-f2 = 'Z'.

modify it index 4.

loop at it.

write: / it-f1, it-f2.

endloop.

loop at it.

it-f1 = it-f1 * 2.

modify it.

endloop.

skip.

loop at it.

write: / it-f1, it-f2.

endloop.

it-f2 = 'X'.

modify it transporting f2 where f1 <> 10.

skip.

loop at it.

write: / it-f1, it-f2.

endloop.