#include<iostream> #include<cmath> using namespace std; int main() { float s; int b, x = 1000 , n, c, i, j, d, l, a[5000]; for (s = 0, n = 1; n <= 5000; n++) { s = s + log10((2 * n + 1) / n); if (s > x + 1) break; } for (i = 0; i <= x + 5; i++) a = 0; for (c = 1, j = n; j >= 1; j--) { d = 2 * j + 1; for (i = 0; i <= x + 4; i++) { a = c / d; c = (c%d) * 10 + a[i + 1]; } a[x + 5] = c / d; for (b = 0, i = x + 5; i >= 0; i--) { a = a * j + b; b = a / 10; a = a % 10; } a[0] = a[0] + 1; c = a[0]; } for (b = 0, i = x + 5; i >= 0; i--) { a = a * 2 + b; b = a / 10; a = a % 10; } cout << a[0] << "."; for (l = 10, i = 1; i <= x; i++) { cout << a; l++; } cout << endl; /* cin.clear(); cin.sync(); cin.get(); */ return 0; }