#include <iostream>
#include <algorithm>
#include <cstring>
#include <vector>
using namespace std;
const int N = 1000010;
vector<int> Alice,Bob;
int k;
string s;
int main()
{
    cin >> k;
    cin.get(); // 接受空字符
    getline(cin,s); 
    s += '.';
    string temp = "";
    for (int i = 0 ; i < s.size() ; i ++)
    {

        if (!isalpha(s[i])) //如果s[i]不是一个字母，那么s[i-1]之前的就是一个单词
        {
            if(temp == "Alice")  Alice.push_back(i - temp.size() );
            else if(temp == "Bob") Bob.push_back(i - temp.size() );
            temp = "";
        }
        else temp += s[i];
    }
    int lp = 0 , rp = 0;
    long long ans = 0;
    int la = Alice.size();
    int lb = Bob.size();
    for (int i = 0 ; i < la ; i ++)
    {
        while (lp < lb &&Bob[lp] < Alice[i] - 3 - k) lp ++;
        while (rp < lb &&Bob[rp] <= Alice[i] + 5 + k) rp ++;
        if (rp - lp > 0) ans += rp - lp;
    }
    cout << ans << endl;
    return 0;

}