Make Value Groups Contiguous

One operation chooses two different values x and y and replaces every x in the array with y simultaneously. In the end, all occurrences of each value must lie in one contiguous block; find the minimum number of operations. You cannot change just one occurrence, nor delete elements.

输入格式

The first line contains n; the second line contains the array. This site uses 1≤n≤200000, −10^9≤element≤10^9.

输出格式

Output a single integer, the answer.

样例 1

输入：

4
1 2 3 1

输出：

2

样例 2

输入：

3
1 2 3

输出：

0

样例 3

输入：

6
1 2 1 3 4 3

输出：

2

样例说明

The answers are 2, 0 and 2. The first example is not only about handling the repeated 1s; the 2 and 3 sandwiched between the two 1s must also be merged in the end.