Uses
CRT;
Var
s, a, b, c: real;
begin
write('a,b,c: ');
readln(a, b, c);
s := sin(a + b) - 0.5 * c;
write('S:=', s);
case round(int(sin(a + b) - 0.5 * c)) mod 4 of
0:
s := int(sin(a + b) - 0.5 * c);
1:
s := frac(sin(a + b) - 0.5 * c);
end;
writeln;
write('S:=', s);
end.