I know to make the problem, but y got a wrong answer.
I don't know how to write with 2 decimals. I tryed in C and C++ - fprintf("%f.2",v[i]); setprecision(4) -. But it dosen't worck. Shall I try in Pascal? :)

try this:
  printf("%.2f", x); //for float
  printf("%.2lf", x); //for double
  printf("%.2Lf", x); //for long double

Pascal variant is
writeln(x:0:2);