#include <bits/stdc++.h>   using namespace std;   int n, m;   long long f(const string& s) {     long long res = 0;     for (int i = 0; i + 1 < s.size(); ++i) {       if (s[i] != s[i + 1]) {         res += (m - 1) * (n - i - 1);       }     }     return res;   }   long long g(const string& s) {     long long res = 0;     for (int i = 0; i + 1 < s.size(); ++i)       if (s[i] != s[i + 1]) {         int j = i + 1;         while (j + 1 < s.size() && s[j + 1] == s[j - 1]) ++j;         long long l = j - i + 1;         res += l * (l - 1) / 2;         i = j - 1;       }     return res;   }   int main() {     string s;     cin >> n >> m >> s;     long long res = n * (m - 1) + f(s);     reverse(s.begin(), s.end());     res += f(s) - g(s);     cout << res << endl;     return 0;   }   