CF266A.Stones on the Table

There are n stones on the table in a row, each of them can be red, green or blue. Count the minimum number of stones to take from the table so that any two neighboring stones had different colors. Stones in a row are considered neighboring if there are no other stones between them.

桌子上有 n 颗石头排成一行，每颗石头的颜色为红色、绿色或蓝色中的一种。求最少需要从桌上拿走多少颗石头，使得任意两颗相邻的石头颜色均不相同。若两颗石头之间没有其他石头，则称它们为相邻的。

The first line contains integer n (1 ≤ n ≤ 50) — the number of stones on the table.

The next line contains string s, which represents the colors of the stones. We'll consider the stones in the row numbered from 1 to n from left to right. Then the i-th character s equals "R", if the i-th stone is red, "G", if it's green and "B", if it's blue.

第一行包含一个整数 $n$（$1 \leq n \leq 50$）—— 表示桌上的石头数量。

下一行包含字符串 $s$，表示石头的颜色。我们将从左到右依次将石头编号为 $1$ 到 $n$。若第 $i$ 个石头为红色，则 $s$ 的第 $i$ 个字符为 "R"；若为绿色，则为 "G"；若为蓝色，则为 "B"。

Print a single integer — the answer to the problem.

输出一个整数——该问题的答案。