// (⁠◕⁠ᴗ⁠◕⁠✿⁠) // #pragma GCC target("avx2") #pragma GCC optimize("O3") #pragma GCC optimize("unroll-loops") #include #define rep(i, n) for (ll i = 0; i < (n); i++) #define srep(i, s, n) for (ll i = s; i < (n); i++) #define len(x) ((int)(x).size()) #define all(x) (x).begin(), (x).end() using namespace std; template using vc = vector; template using vv = vc>; template using vvv = vv>; using vi = vc;using vvi = vv; using vvvi = vv; using ll = long long;using vl = vc;using vvl = vv; using vvvl = vv; using ld = long double; using vld = vc; using vvld = vc; using vvvld = vc; using uint = unsigned int; using ull = unsigned long long; const ld pi = acos(-1.0); const int inf = 0x3f3f3f3f; const ll INF = 0x3f3f3f3f3f3f3f3f; // const ll mod = 1000000007; const ll mod = 998244353; inline bool inside(ll y, ll x, ll H, ll W) {return 0 <= (y) and (y) < (H) and 0 <= (x) and (x) < (W); } #define debug(var) do{std::cout << #var << " : \n";view(var);}while(0) template void view(T e){cout << e << endl;} template void view(const vc& v){for(const auto& e : v){ cout << e << " "; } cout << endl;} template void view(const vv& vv){ for(const auto& v : vv){ view(v); } } int main(){ int N; cin >> N; string S; cin >> S; int ans = 0; rep(j, N - 2) rep(i, j - 1) if (S[i] == S[j]){ srep(a, i + 1, j) if (S[i] != S[a]){ srep(c, j + 2, N) if(S[i] != S[c] && S[a] != S[c]){ srep(b, j + 1, c) if (S[i] != S[b] && S[a] != S[b] && S[c] != S[b]){ ans++; } } } } cout << ans << endl; }