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diff --git a/mat/advent/0/fakulteta.c b/mat/advent/0/fakulteta.c
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+// shamelessly ukradeno iz
+// https://www.geeksforgeeks.org/factorial-large-number/
+// Maximum number of digits in output 
+#include <stdio.h>
+#include <stdlib.h>
+#define MAX 5000 
+int multiply(int x, int res[], int res_size); 
+
+// This function finds factorial of large numbers 
+// and prints them 
+void factorial(int n) 
+{ 
+	int res[MAX]; 
+
+	// Initialize result 
+	res[0] = 1; 
+	int res_size = 1; 
+
+	// Apply simple factorial formula n! = 1 * 2 * 3 * 4...*n 
+	for (int x=2; x<=n; x++) 
+		res_size = multiply(x, res, res_size); 
+
+	fprintf(stdout, "Factorial of given number is \n");
+	for (int i=res_size-1; i>=0; i--) 
+		fprintf(stdout, "%d", res[i]);
+	fprintf(stdout, "\n");
+} 
+
+// This function multiplies x with the number  
+// represented by res[]. 
+// res_size is size of res[] or number of digits in the  
+// number represented by res[]. This function uses simple  
+// school mathematics for multiplication. 
+// This function may value of res_size and returns the  
+// new value of res_size 
+int multiply(int x, int res[], int res_size) 
+{ 
+	int carry = 0;  // Initialize carry 
+
+	// One by one multiply n with individual digits of res[] 
+	for (int i=0; i<res_size; i++) 
+	{ 
+		int prod = res[i] * x + carry; 
+
+		// Store last digit of 'prod' in res[]   
+		res[i] = prod % 10;   
+
+		// Put rest in carry 
+		carry  = prod/10;     
+	} 
+
+	// Put carry in res and increase result size 
+	while (carry) 
+	{ 
+		res[res_size] = carry%10; 
+		carry = carry/10; 
+		res_size++; 
+	} 
+	return res_size; 
+} 
+
+// Driver program 
+int main(int argc, char ** argv) {
+	if(argc != 2) {
+		fprintf(stderr, "uporaba: %s stevilka\n", argv[0]);
+		return 1;
+	}
+	factorial(atoi(argv[1])); 
+	return 0; 
+}