Happy new year^_^!!! YYY as XXX's best friend, she will give XXX a gift on New Year's day. This gift is a string! Yes, the gift is a string of length n (n is an even number). Because XXX is a good student who loves learning, she will love this gift. This string consists of only two characters' x 'and' y '. But XXX is an obsessive-compulsive disorder! He cant't stand the thing which is single. Now XXX needs to change her gift into a string with the number of 'x' equal to the number of 'y'. Each modification is to change 'x' to 'y' or 'y' to 'x'. But she is busy with the final review recently. She wants to ask you to help her solve this problem. You need to find the minimum number of modifications so that the number of 'x' in the string is equal to the number of 'y'.
Note: The number of changes may be zero
输入描述:
Enter a positive integer n in the first line
In the second line, enter a string containing only the characters' x 'and' y '
The range of n is 1 < = n < = 100
输出描述:
Output a number k ,which means the minimum number of modifications in a single line.