program utf ;
var a,b,c,d,s1,k:integer;
s:real;
begin
writeln ('a=');readln(a);
writeln ('b=');readln(b);
writeln ('c=');readln(c);
writeln ('d=');readln(d);
if a>0 then begin
s1:=s1+a;
k:=k+1;
end;
if b>0 then begin
s1:=s1+b;
k:=k+1;
end;
if c>0 then begin
s1:=s1+c;
k:=k+1;
end;
if d>0 then begin
s1:=s1+d;
k:=k+1;
end;
s:=s1/k;
end.2