为什么??????????

为什么结果是
TASK: test
LANG: PASCAL

Compiling...
Compile: OK

Executing...
Execution error: Your program (`test') exited with exit status `2'
when presented with test case 1, shown below.

Your program's exit status might indicate Pascal Runtime Error 2. Here
is the message for that Runtime Error:
File not found: You can get this error when you tried to do an
operation on a file which doesn't exist.


----- Test Case 1 ------
1 1
----------------------------

Your program printed data to stdout. Here is the data:
-------------------
Runtime_error_2_at_$08048108__$08048108

-------------------
Run time error 2: File not found: You can get this error when you
tried to do an operation on a file which doesn't exist.
-------------------
Full Test Data   Full Answer----------------------------
Read this if your program works on your computer but not the grader. Do not write a letter to the coaches until you have tried these techniques!

Thanks for your submission!

我的程序是(第一题的)
program ride;
var input,out:text;
  ch:char;
  s1,s2:longint;
begin
assign(input,'ride.in');
assign(output,'ride.out');
reset(input);
rewrite(output);
read(input,ch);
s1:=1;
s2:=1;
while ch in['A'..'Z'] do
begin
s1:=s1*(ord(ch)-64);
read(input,ch);
end;
while ch in [' ',#13,#10] do
read(input,ch);
while ch in['A'..'Z'] do
begin
s2:=s2*(ord(ch)-64);
read(input,ch);
end;
if s1 mod 47=s2 mod 47 then writeln(output,'GO')
else writeln(output,'STAY');
close(input);
close(output);
end.

USACO使用的是Free Pascal编译器，在该编译器中，out是保留字

我刚才把你的程序上传了，通过！