program product;
const
     m = 400;
var
   p,x:extended;
   n:word;

begin
     product :=1.0;
     for n:=2 to m do
     begin
          x:=sqr(1.0/n);
          if odd(n) then
             product:=product*(1.0 - x)
          else
              product := product * (1.0 + x);
     end
     writeln('proizvedenie dlya 2 <= n <= ', m,':');
     writeln;
     writeln('p(1+(-1)^n/n^2) = ', product);
     writeln;
     writeln('nagmite Enter: ');
     readln;
end.