#include <iostream>
#include <string>
#include <vector>

int count1 = 0;
void generateSubsequences(const std::string& str, int index, std::string current, int count) {
    if (count == 5) {
    	if(current[0] == current[2] && current[1] != current[2] && current[1] != current[3] && current[1] != current[4] && current[2] != current[3] && current[2] != current[4] && current[3] != current[4]){
    		count1++;
        return;
    	}
    }
    if (index >= str.size()) return;
    generateSubsequences(str, index + 1, current + str[index], count + 1);
    generateSubsequences(str, index + 1, current, count);
}

int main() {
	int n;
	std::cin>>n;
    std::string s;
    std::cin >> s;
    generateSubsequences(s, 0, "", 0);
    std::cout << count1 << std::endl;
    return 0;
}