var a,b,c,d,s: integer;
begin
readln(a,b,c,d);
s:=0;
if a>0 then s:=s+a;
if b>0 then s:=s+b;
if c>0 then s:=s+c;
if d>0 then s:=s+d;
writeln(s);
end.
var a,b,c,d,s: integer;
begin
readln(a,b,c,d);
s:=0;
if a>0 then s:=s+a;
if b>0 then s:=s+b;
if c>0 then s:=s+c;
if d>0 then s:=s+d;
writeln(s);
end.