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#include <bits/stdc++.h>
using namespace std;

const long long MOD = 998244353;

void rec(const string &s, long long i, string cur, unordered_map<string, long long> &sc) {
    if(i == s.size()){
        if(!cur.empty()) sc[cur]++;
        return;
    }
    rec(s, i + 1, cur, sc);
    rec(s, i + 1, cur + s[i], sc);
}

long long count(const string &s) {
    unordered_map<string, long long> sc;
    rec(s, 0, "", sc);
    long long res = 0;
    for (const auto &p : sc) {
        if(p.second >= 2) res++;
    }
    return res % MOD;
}

int main(){
    cin.tie(0)->sync_with_stdio(0);

    long long n, q;
    cin >> n >> q;
    string s;
    cin >> s;

    cout << count(s) << "\n";

    for (long long i = 0; i < q; i++){
        long long pos;
        char c;
        cin >> pos >> c;
        s[pos - 1] = c;
        cout << count(s) << "\n";
    }
}