I have mended some wrong but still WA?
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var s1,s2,s3,s4,a1,a2,b1,b2,t:real;
    total:longint;
function sov(aa:real):real;
var x,y:real;
begin
     y:=frac(aa)*100;
     x:=trunc(aa);
     sov:=x+y/60;
end;
begin
     read(s1,s2,s3,s4);
     a1:=sov(s1);
     b1:=sov(s2);
     a2:=sov(s3);
     b2:=sov(s4);
     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(t);
end.
What's the local time if there is not in one day?