It is vr easy.
Var i,j,k:longint;
    a:array[0..1000000] of shortint;
Begin
 readln(k);
 for i:=1 to k do begin readln(a[i],j); inc(a[i],j); end;
 for i:=k downto 1 do
  while a[i]>9 do
   begin dec(a[i],10); inc(a[i-1],1); end;
 i:=0;
 while (a[i]=0)and(i<1) do inc(i);
 for j:=i to k do write(a[j]); writeln;
End.