foo.cc:3:13: error: too many decimal points in number
 var a:array[1..1000]of longint;
             ^~~~~~~
foo.cc:1:1: error: 'program' does not name a type
 program kifhjk;
 ^~~~~~~
foo.cc:3:1: error: 'var' does not name a type; did you mean 'char'?
 var a:array[1..1000]of longint;
 ^~~
 char
foo.cc:5:1: error: 'n' does not name a type
 n,i,j,k,sum:longint;
 ^
foo.cc:7:1: error: 'begin' does not name a type
 begin
 ^~~~~
foo.cc:11:1: error: expected unqualified-id before 'for'
 for i:= 1 to n do
 ^~~
foo.cc:15:1: error: expected unqualified-id before 'for'
 for i:=n-1 downto 1 do
 ^~~
foo.cc:21:1: error: 'sum' does not name a type; did you mean 'enum'?
 sum:=0;
 ^~~
 enum
foo.cc:23:1: error: expected unqualified-id before 'for'
 for i:=1 to n do
 ^~~
foo.cc:27:8: error: expected constructor, destructor, or type conversion before '(' token
 writeln(sum);
        ^
foo.cc:29:1: error: 'end' does not name a type; did you mean 'enum'?
 end.
 ^~~
 enum

自豪的采用HydroJudge(https://github.com/hydro-dev/Hydro)进行评测。