added other cases for input being smaller than 16

src/conversionOfNumbers/conversionOfNumbers.c

@@ -60,6 +60,12 @@ char* convertIntToHex(int input){
         rest = input % 16;
         input /= 16;
         switch(rest){
+            case 10: result[length - 1] = 'A'; break;
+            case 11: result[length - 1] = 'B'; break;
+            case 12: result[length - 1] = 'C'; break;
+            case 13: result[length - 1] = 'D'; break;
+            case 14: result[length - 1] = 'E'; break;
+            case 15: result[length - 1] = 'F'; break;
             default: result[length - 1] = rest + '0'; break;
         }
         length--;