#include <bits/stdc++.h>
using namespace std;
void printprecise(double l, long long int precision) {
  std::cout << std::fixed;
  std::cout << std::setprecision(precision);
  std::cout << l;
}
long long int ncr(long long int n, long long int k) {
  long long int C[n + 1][k + 1];
  long long int i, j;
  for (i = 0; i <= n; i++) {
    for (j = 0; j <= min(i, k); j++) {
      if (j == 0 || j == i)
        C[i][j] = 1;
      else
        C[i][j] = C[i - 1][j - 1] + C[i - 1][j];
    }
  }
  return C[n][k];
}
long long int power_wm(long long int x, long long int y, long long int p) {
  long long int res = 1;
  x = x % p;
  while (y > 0) {
    if (y & 1) res = (res * x) % p;
    y = y >> 1;
    x = (x * x) % p;
  }
  return res;
}
long long int power(long long int x, long long int y) {
  long long int res = 1;
  while (y > 0) {
    if (y & 1) res = (res * x);
    y = y >> 1;
    x = (x * x);
  }
  return res;
}
long long int root(long long int x, vector<long long int> &roots) {
  if (roots[x] != x) roots[x] = root(roots[x], roots);
  return roots[x];
}
void unoin(long long int p, long long int q, vector<long long int> &roots,
           vector<long long int> &rank) {
  long long int rp = root(p, roots);
  long long int rq = root(q, roots);
  if (rank[rq] < rank[rp]) {
    roots[rq] = rp;
  } else if (rank[rp] > rank[rq]) {
    roots[rp] = rq;
  } else {
    roots[rp] = rq;
    rank[rq]++;
  }
}
long long int dig_sum(long long int n) {
  long long int s = 0;
  while (n) {
    s += n % 10;
    n /= 10;
  }
  return s;
}
long long int gcd(long long int a, long long int b) {
  if (a < b) {
    a = a + b;
    b = a - b;
    a = a - b;
  }
  if (b == 0) return a;
  return gcd(b, a % b);
}
long long int toD(long long int x, long long int y, long long int m) {
  return x * m + y % m;
}
pair<long long int, long long int> twoD(long long int p, long long int m) {
  return (make_pair(p / m, p % m));
}
vector<long long int> dist;
vector<vector<long long int> > g;
void dfs(long long int p) {
  if (dist[p] != -1) {
    return;
  }
  dist[p] = 0;
  long long int maxd = -1;
  for (long long int i = 0; i < g[p].size(); i++) {
    dfs(g[p][i]);
    maxd = max(maxd, dist[g[p][i]]);
  }
  dist[p] = maxd + 1;
}
vector<long long int> fact;
void calfact() {
  fact[0] = 1;
  for (long long int i = 1; i < 1000001; i++) {
    fact[i] = (fact[i - 1] * i) % 998244353;
  }
}
int main() {
  ios::sync_with_stdio(false);
  cin.tie(0);
  cout.tie(0);
  long long int n;
  cin >> n;
  string s;
  cin >> s;
  s = ' ' + s;
  long long int c = 0;
  vector<long long int> last_a(n + 1), last_b(n + 1);
  for (long long int i = 1; i < n + 1; i++) {
    last_b[i] = last_b[i - 1];
    last_a[i] = last_a[i - 1];
    if (s[i - 1] == 'A') {
      last_a[i] = i - 1;
    } else {
      last_b[i] = i - 1;
    }
    if (s[i] == 'A') {
      c += last_a[i];
      if (last_b[i] > 0 and last_b[i] < last_a[i]) {
        c--;
      }
    } else {
      c += last_b[i];
      if (last_a[i] > 0 and last_a[i] < last_b[i]) {
        c--;
      }
    }
  }
  cout << c;
  return 0;
}
