Color Sequence
1000ms 65536K
描述
You are given a integer sequence c of length n, ci denotes the ith color in the sequence c.
We define a color sequence is legal only if it merely contains colors that appear even number of times.
For example, sequence 0,1,0,1 is legal because both color 1 and 0 appear 2 times, and 2 is an even number. And sequence 0,1,0is illegal because color 1 only appear 1 time, and 1 is not an even number.
Now, you need to figure out how many consecutive subsequence of c that is a legal color sequence.
输入：
The first line contains one integer n(1≤n≤10的6次方), the length of the sequence c.
The second line contains n integer, the ith integer denotes the ith color, )ci(0≤ci≤20).
输出：
Print one integer as the answer.
样例输入：
3 1 1 1
样例输出：
2
--------------------------------------------------------------------------------------------------------
描述：
给你一个长度为nn的整数序列c，ci代表序列c的第i个颜色。
我们定义当一个序列只由偶数个颜色组成时它是合法的。
例如，序列0,1,0,1是合法的，应为颜色1，0都出现了2次，且2是一个偶数。而数列010是不合法的，因为1只出现了1次，1不是偶数。
现在，你需要知道有多少个c的子序列是合法的。
输入：
第一行由一个整数n(1≤n≤10的6次方)组成，为c的长度。
第二行有n个整数，第i个整数表示i的颜色ci(0≤ci≤20)。
输出：
输出一个整数答案。
样例输入：
3 1 1 1
样例输出：
2