I always get runtime error on problem (#253A) I can't find the reason for this message.

In Python

import sys n,m=map(int, raw_input().split())

i=min(n,m)

print (n-i)*"B"+i*"GB" +(m-i)*"G"

in pascal

uses sysutils,math; var b,g,i,x:longint;

s,p,q:string;

begin read(b,g);

s:='';

i:=min(b,g);

for x:=1 to i do

s:=s+'BG';

for x:=1 to (b-i) do

s:=s+'B';

for x:=1 to (g-i) do

s:=s+'G';

writeln(s);

end.
On my computers the code works well what goes wrong here?