class point{ public: char key; long count; point(char key,long count){ this->key = key; this->count = count; } };

int main() { std::vector _v; long count = 1; int n; scanf("%d",&n); char str[n]; std::cin >> str; char ch = str[0];

for(int i = 1; i <= n; i++) {
    if (ch == str[i])
        count += 1;
    else
    {
        _v.push_back(point(ch,count));
        count = 1;
        ch = str[i];
    }
}
count = 0;
for(auto p : _v)
    count += (p.count * (p.count + 1)) / 2;

for(int i = 1; i < _v.size() - 1; i++) {
    if (_v[i - 1].key == _v[i + 1].key && _v[i].count == 1)
        count += std::min(_v[i - 1].count,_v[i + 1].count);
}


printf("%ld\n",count);
return 0;

}