addition base case to tenscolumns

src/addition.c

@@ -12,6 +12,6 @@ unsigned int addition(unsigned int a, unsigned int b) {
     int nc[1] = {0};
 
     full_adder(s, nc, a, b, 0);
-    
-    return (unsigned int) s[0];
+
+    return (unsigned int) s[0] ^ (nc[0] << 1);
 }