#include<boost/multiprecision/mpfr.hpp>
#include<iostream>

using namespace boost::multiprecision;
using namespace std;

constexpr unsigned DIGIT = 100'000'001;
using my_mpfr_float = number<mpfr_float_backend<DIGIT>>;

my_mpfr_float operator"" _big(unsigned long long n) {
    return my_mpfr_float(n);
}

int main() {
    my_mpfr_float a = 1_big;
    my_mpfr_float b = 1_big / sqrt(2_big);
    my_mpfr_float t = 1_big / 4_big;
    my_mpfr_float p = 1_big;

    for (my_mpfr_float n = 0_big, lim = log2(DIGIT); n < lim; n++) {
        my_mpfr_float pa = a, pb = b, pt = t, pp = p;
        a = (pa + pb) / 2_big;
        b = sqrt(pa * pb);
        t = pt - pp * pow(pa - a, 2_big);
        p = 2_big * pp;
    }

    cout << setprecision(DIGIT) << pow(a + b, 2_big) / (4_big * t) << endl;
}