This is my program:
var
  i:longint;
  a,b:real;

procedure init;
begin
  read(a);
  read(b);
  a:=a/100;
  b:=b/100;
end;

procedure work;
begin
  i:=0;
  repeat
    inc(i);
  until abs(trunc(i*a)-trunc(i*b))>=1;
end;

procedure print;
begin
  writeln(i);
end;

begin
  init;
  work;
  print;
end.

This is my program:
var
i:longint;
a,b:real;

procedure init;
begin
read(a);
read(b);
a:=a/100;
b:=b/100;
end;

procedure work;
begin
i:=0;
repeat
inc(i);
until abs(trunc(i*a)-trunc(i*b))>=1;{   see here   } (****)
end;

procedure print;
begin
writeln(i);
end;

begin
init;
work;
print;
end.


Your program have mistake
(****)
this correct version:
  repeat
    inc(i);
    c := trunc(i*a);
    d := i*b;
    if frac(d) = 0 then d := d - 1
    Else d := trunc(d);
  until d > c;

I have this program and got AC 0.015s and 373KB :))

What is my mistake? Could you tell me?

Try find mistake independent... :))) and prove(****) too

Becasue ,if(tranc(i*b)==i*b),in the case,it's possble have mistake!

Use SINGLE type - you'll get AC!