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#include <iostream>
#include <vector>
#include <set>

using namespace std;

const long long MOD = 998244353;

int n;
string word;

long long plusMod(long long a, long long b) {
    return (a + b) % MOD;
}

void compute() {
    vector<long long> total(n);
    vector<long long> single(6);
    vector<bool> notFirst(6);
    vector<long long> last(6);
    vector<vector<bool>> afterLast(6, vector<bool>(6, false));

    for (int i = 0; i < n; i++) {
        int letter = word[i] - 'a';

        if (i == 0) {
            total[i] = 1;
        } else {
            total[i] = 2 * total[i - 1];
            if (notFirst[letter]) {
                if (last[letter] > 0) {
                    total[i] = MOD + total[i] - total[last[letter] - 1];
                }
            } else {
                total[i] = total[i] + 1;
            }
            total[i] = total[i] % MOD;
        }
        if (!notFirst[letter]) {
            single[letter] = 1;
        }
        for (int j = 0; j < 6; j++) {
            if (afterLast[letter][j]) {
                single[letter] = single[letter] + single[j];
            }
        }
        single[letter] = single[letter] % MOD;
        for (int j = 0; j < 6; j++) {
            if (letter != j) {
                afterLast[j][letter] = true;
            } else {
                for (int k = 0; k < 6; k++) {
                    afterLast[letter][k] = false;
                }
            }
        }
        last[letter] = i;
        notFirst[letter] = true;

        // cout << "Leter: " << letter
        //     << " A: " << single[0]
        //     << " B: " << single[1]
        //     << " C: " << single[2]
        //     << " D: " << single[3]
        //     << " E: " << single[4]
        //     << " F: " << single[5]
        //     << " total: " << total[i] << endl;
    }
    long long result = total[n - 1];
    for (int j = 0; j < 6; j++) {
        result = MOD + result - single[j];
    }

    cout << result % MOD << endl;
}

int main() {
    ios::sync_with_stdio(false);
    cin.tie(nullptr);

    int q;
    cin >> n >> q;

    cin >> word;

    vector<pair<int, char>> changes(q);

    for (int i = 0; i < q; i++) {
        cin >> changes[i].first >> changes[i].second;
    }

    compute();
    for (int i = 0; i < q; i++) {
        // if (i % 1000 == 0)
        //     cout << i << endl;
        word[changes[i].first - 1] = changes[i].second;
        compute();
    }

}