#include <iostream>

uint32_t mask = 0, m;

int main(){
	int N, ans = 0;
	std::string S;
	std::cin >> N >> S;
	for(char & c : S) c -= 'A';
	for(int n1 = 0; n1 < N - 4; ++n1){
		m = 1U << S[n1];
		mask |= m;
		for(int n2 = n1 + 1; n2 < N - 3; ++n2){
			m = 1U << S[n2];
			if((mask & m) != 0) continue;
			mask |= m;
			for(int n3 = n2 + 1; n3 < N - 2; ++n3){
				if(S[n1] != S[n3]) continue;
				for(int n4 = n3 + 1; n4 < N - 1; ++n4){
					m = 1U << S[n4];
					if((mask & m) != 0) continue;
					mask |= m;
					for(int n5 = n4 + 1; n5 < N - 0; ++n5){
						m = 1U << S[n5];
						if((mask & m) != 0) continue;
						ans ++;
					}
					mask ^= (1U << S[n4]);
				}
			}
			mask ^= (1U << S[n2]);
		}
		mask ^= (1U << S[n1]);
	}
	std::cout << ans << std::endl;
}