/* Tối ưu code problem 266A  https://codeforces.com/problemset/problem/266/A */
/* code dao la dam me :v */

#include <iostream>
#include <string>

using namespace std;

int main()
{
    int n;
    cin >> n;
    string s;
    cin >> s;
    int dem = 0;
    for (int i = 1; i < n; i++)
    {
        if (s[i - 1] == s[i])
        {
            if (s[i] == 'R')
            {
                 ++dem;
            }
            else
            {
                if(s[i]=='G')
                {
                    ++dem;
                }
            }
        }
        else
        {
            if(s[i]=='B')
                ++dem;
        }
    }
    cout << dem;
    return 0;
}