//确保AC #include #include using namespace std; int a[100010] = {1}; int len = 0; int n; void f(int x) { int k = 0; for(int i = 0; i <= len; i++) { a[i] = a[i] * x + k; k = 0; if(a[i] >= 10000) { k = a[i] / 10000; a[i] %= 10000; } } while(k != 0) { a[++len] = k % 10000; k = k / 10000; } return; } int main() { cin >> n; for (int i = 1; i <= n; i++) f(i); cout << a[len]; for(int i = len - 1; i >= 0; i--) printf ("%04d", a[i]); return 0; }