uses crt;

var a,b,c:real;

begin

clrscr;

repeat

write('Nhap a='); readln(a);</p><p>write('Nhap b='); readln(b);</p><p>write('Nhap c='); readln(c);</p><p>until (a>0) and (b>0) and (c>0);</p><p>if (a+b>c) and (a+c>b) and (b+c>a) then </p><p>begin</p><p>writeln('La do dai ba canh cua tam giac');

writeln('Chu vi tam giac la: ',a+b+c:4:2);

end

else writeln('Khong phai la do dai 3 canh cua tam giac');

readln;

end.