#include <stdio.h>
// Function to calculate factorial
int factorial(int n);
int main() {
int num;
// Input from user
printf("Enter a non-negative integer: ");
scanf("%d", &num);
// Check for negative input
if (num < 0) {
printf("Factorial is not defined for negative numbers.\n");
} else {
// Calculate and display factorial
int result = factorial(num);
printf("Factorial of %d = %d\n", num, result);
}
return 0;
}
// Recursive function to calculate factorial
int factorial(int n) {
// Base case: factorial of 0 is 1
if (n == 0) {
return 1;
} else {
// Recursive case: n! = n * (n-1)!
return n * factorial(n - 1);
}
}