Помогите найти ошибку

program pr1;
var a, b, m,: integer;
p: real;
begin
m:=0;
readln (a,b);
p:= b-a;
if p mod 2 = 0 then
m:= p/2;
end;
if p mod 2 = 1 then
m:=(p-1)/2;
writeln(m);
end.

source.pas(4,13) Fatal: Syntax error, "identifier" expected but ":" found
Error: /usr/bin/ppcx64 returned an error exitcode