diff --git a/src/gcd.c b/src/gcd.c
index b083f1b..91afd01 100644
--- a/src/gcd.c
+++ b/src/gcd.c
@@ -3,6 +3,8 @@
 const int n = 1000;
 
 unsigned int Euclidean_gcd_rec(unsigned int x, unsigned int y){
+	if (x==0) return y;
+	return Euclidean_gcd_rec(y % x, x);
 }
 
 /*