program a1048;
const nn=500003;
var a:array[0..nn] of byte;
i,j,c,b,n:longint;

procedure mass(i:longint;x:byte);
begin
if i mod 2=0 then a[i div 2]:=(a[i div 2] mod 10)+x*10
else a[i div 2]:=(a[i div 2] div 10)*10+x;
end;

function mas(i:longint):byte;
begin
if i mod 2 =0 then mas:=a[i div 2] div 10
else mas:=a[i div 2] mod 10;
end;

begin
fillchar(a,SizeOf(a),0);
readln(n);
for i:=1 to n do
   begin
   readln(b,c);
   b:=b+c;
   for j:=i downto 1do
      begin
      b:=b+mas(j);
      mass(j,b mod 10);
      b:=b div 10;
      if b=0 then break;
      end;
   end;
for i:=1 to n do
   write(mas(i));
writeln;
end.

>

What a long, slow, big program!