uses crt;
var
z: char;
a, b: real;
label 1;
begin
clrscr;
write('enter FIRST digit: ');  readln(a);
write('enter SECOND digit: '); readln(b);
1:write('enter operation: ');  readln(z);
if (z <> '*') OR (z <> '/') OR (z <> '+') OR (z <> '-') then goto 1;
write('result: ');
if z = '*' then write(a*b);
if z = '/' then write(a/b);
if z = '+' then write(a+b);
if z = '-' then write(a-b);
readln;
end.