📅  最后修改于: 2022-03-11 14:52:05.959000             🧑  作者: Mango
program Pr115_3;
var
k, n : integer;
suma : real;
begin
readln(n);
suma := 0;
for k := 1 to n do
suma := suma + 1 / sqr(2*k+1);
writeln(suma);
readln;
end.