program t1070;
var a1,b1,a2,b2,t:extended;
    total:longint;
begin
     read(a1,b1,a2,b2);
     if a1>b1 then b1:=b1+24
        else if b2-a2>11 then begin t:=b2; b2:=a2+24; a2:=t; end;
     if a2>b2 then b2:=b2+24
        else if b1-a1>5 then begin t:=b1; b1:=a1+24; a1:=t; end;
     total:=trunc(abs((b1-a1)-(b2-a2))/2);
     writeln(total);
     readln;
     readln;
end.
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What's the local time if there is not in one day?