var n,i,j:word;a:array[0..9,0..9]of longint;begin
repeat
repeat read(a[0,i]);inc(i)until eoln;n:=i-1;for i:=1to n do for j:=0to n-i do
a[i,j]:=a[i-1,j+1]-a[i-1,j];a[n,1]:=a[n,0];for i:=n-1downto 0do a[i,n-i+1]:=a[i,n-i]+a[i+1,n-i];writeln(a[0,n+1])until 1=0end.