Program Btt;
Uses crt;
Var a,b,c,d: longint;
Begin
Clrscr;
Write('Nhap 4 so a, b, c, d: '); Readln(a,b,c,d);
If (c=0) and (d=0) then Write('a = ',a,', b = ',b);
If (c=0) and (d<>0) then Write('c/d = ',c,'/',d);
If (c<>0) and (d<>0) then
Begin
Write('a/b = ',a,'/',b);
Writeln;
Write('a/b+c/d = ',a*d+b*c,'/',b*d);
Writeln;
Write('a/b-c/d = ',a*d-b*c,'/',b*d);
Writeln;
Write('a/n . c/d = ',a*c,'/',b*d);
Writeln;
Write('a/b : c/d = ',a*d,'/',b*c);
End;
Readln
End.