using namespace std;
otherwise you can do this with the help of recursive fuction . I f you in need then I’ll give you the sollution.
You can’t do this question this way since n<=100 and 100! Has 157 digits , which is way greater than capacity of long and long long , you will have to make an array of digits and fill it one by one by multiplying and adding the carry like you studied multiplication in class 2 or 3
Eg. to calculate 14*15 you will have to multiply 4 by 15 give 6 as carry and multiply 1 by 15 and then add 6 resulting in 210