#Find the factorial of a number
# take input from the user
num = as.integer(readline(prompt="Enter a number: "))
factorial = 1

# check is the number is negative, positive or zero
if(num < 0) {
    print("Sorry, factorial does not exist for negative numbers")
} else if(num == 0) {
    print("The factorial of 0 is 1")
} else {
    for(i in 1:num) {
        factorial = factorial * i
    }
    print(paste("The factorial of", num ,"is",factorial))
}
Output

Enter a number: 8
[1] "The factorial of 8 is 40320"