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#include <iostream> long double f(long double a) { long double factorial = 1; while (a > 1) { factorial *= a; a--; } return factorial; } int main() { long double n = 0; std::cin >> n; long double s = 0; long double nf = f(n); for (int k = 2; k <= n; k++) { s += nf/f(n-k); } std::cout.precision(0); std::cout << std::fixed << s << "\n"; return 0; }