const
 maxn=1000000;

var
 i,n:integer;
 data:array[1..maxn]of integer;

Procedure Init;
var
 a,b:integer;
begin
  readln(n);
 for i:=1 to n do
  begin
   readln(a,b);
   data[i]:=a+b;
  end;
end;

Procedure Main;
begin
 for i:=n downto 1 do
  begin
   inc(data[i-1],data[i] div 10);
   data[i]:=data[i] mod 10;
  end;
 if data[1]>=10 then begin write(data[1] div 10);data[1]:=data[1] mod
10; end;
 for i:=1 to n do
  write(data[i]);
end;

begin
 Init;
 Main;
end.

I haven't looked into your program to find the reason of WA, but you
use array of 2 mb. size - don't you think it is going to be MLE
anyway? BTW, there is a way to solve this problem without any arrays
at all.