ac wa 9999999999999999999999999999999999999999999999999999999999999999999 0 #include<iostream> #include<cstdio> using namespace std; int main(){ int n; double f=1; cin >> n; for(int i=1;i<=n;i++){ int x=1; for(int j=1;j<=i;j++){ x*=j; } if(i%21) f-=1.0/x; else if(i%20) f+=1.0/x; }

#include<bits/stdc++.h>//最优解 using namespace std; double factorial(int n) { double fact = 1; for (int i = 1; i <= n; ++i) fact *= i; return fact; } int main() { int n; double f = 1; cin >> n; for (int i = 1; i <= n; ++i) { double inv_factorial = 1.0 / factorial(i); if (i % 2 == 1) f -= inv_factorial; else f += inv_factorial; } cout << fixed << setprecision(8) << f << endl; return 0; }

#include <iostream> using namespace std; int main(){ int n; cin>>n; double a=1,b=1,c=1; for(int i=1;i<=n;i++){ a=a+1/b; b=b*(i+1); } for(int i=1;i<=n;i=i+2){ if(i>1) c=c*(i-1)*i; a=a-2/c; }

#include<iostream> #include<cstdio> #include<math.h> using namespace std; int main(){ int n, y; double f = 1; cin>>n; for(int i=1;i<=n;i++){ y = 1; for(int x=1;x<=i;x++){ y *= x; } if(i%2 == 0){ f += pow(y, -1); } else if(i%2 == 1){ f -= pow(y, -1); } } printf("%.8f", f); return 0; }

#include <bits/stdc++.h> using namespace std; int jc(int x){ if (x==1) return 1; return x*jc(x-1); } int main(){ }

#include <bits/stdc++.h> using namespace std; int calculate(int n) { long long sum = 1; for (int i = n; i >= 1; i--) { sum *= i; } return sum; } int main() { int n; cin >> n; double f = 1; if (n == 1) { cout << "0.00000000"; return 0; } for (int i = 1; i <= n; i++) { if (i % 2 == 0) { f = f + (1.0 / calculate(i)); } else { f = f - (1.0 / calculate(i)); } } cout << fixed << setprecision(8) << f; }