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#include <algorithm>
#include <bitset>
#include <cmath>
#include <cstdlib>
#include <ctime>
#include <deque>
#include <iostream>
#include <list>
#include <map>
#include <queue>
#include <set>
#include <stack>
#include <string>
#include <vector>

using namespace std;

#define JOIN_(X, Y) X##Y
#define JOIN(X, Y) JOIN_(X, Y)
#define TMP JOIN(tmp, __LINE__)
#define PB push_back
#define SZ(x) int((x).size())
#define REP(i, n) for (int i = 0, TMP = (n); i < TMP; ++i)
#define FOR(i, a, b) for (int i = (a), TMP = (b); i <= TMP; ++i)
#define FORD(i, a, b) for (int i = (a), TMP = (b); i >= TMP; --i)

#ifdef DEBUG
#define DEB(x) (cerr << x)
#else
#define DEB(x)
#endif

template <typename S, typename T> ostream &operator<<(ostream &os, const pair<S, T> &p) {
    os << "(" << p.first << ", " << p.second << ")";
    return os;
}

template <typename T> ostream &operator<<(ostream &os, const vector<T> &vec) {
    os << "[";
    for (int i = 0; i < SZ(vec); ++i) {
        os << vec[i];
        if (i != SZ(vec) - 1) {
            os << ", ";
        }
    }
    os << "]";
    return os;
}

typedef long long ll;
typedef vector<int> vi;
typedef pair<int, int> pii;
typedef unsigned int uint;

const int INF = 1e9 + 9;
const ll MOD = 998244353;

struct Case {
    int n, queries;
    string s;
    vector<ll> rep;
    vector<vector<ll>> uniq;

    ll run_dp() {
        rep.assign(n + 1, 0);
        uniq.assign(n + 1, vector<ll>(6, 0));
        vector<int> last_seen(6);
        FOR(i, 1, n) {
            DEB("=====\n");
            DEB("i=" << i << "\n");
            DEB("s=" << s << "\n");
            int c = s[i - 1] - 'a';
            DEB("s[i-1]=" << s[i - 1] << " c=" << c << "\n");
            // if (i == 1) {
            //     rep[i] = 0;
            //     uniq[i][c] = 1;
            // } else {
            if (last_seen[c] == 0) {
                rep[i] = (rep[i] + 2 * rep[i - 1]) % MOD;
                uniq[i][c] = (uniq[i][c] + 1) % MOD;
                last_seen[c] = i;
            } else {
                rep[i] = (rep[i] + rep[i - 1]) % MOD;
                REP(j, 6) {
                    if (j != c) {
                        uniq[i][c] = (MOD + uniq[i][c] - uniq[last_seen[c]][j]) % MOD;
                    }
                }
            }

            REP(j, 6) {
                if (j == c) {
                    rep[i] = (rep[i] + uniq[i - 1][j]) % MOD;
                    uniq[i][j] = (uniq[i][j] + uniq[i - 1][j]) % MOD;
                } else {
                    uniq[i][c] = (uniq[i][c] + uniq[i - 1][j]) % MOD;
                    uniq[i][j] = (uniq[i][j] + uniq[i - 1][j]) % MOD;
                }
            }
            // }
            DEB("  rep=" << rep << "\n");
            DEB("  uniq=" << uniq << "\n");
        }
        DEB("rep=" << rep << "\n");
        DEB("uniq=" << uniq << "\n");
        DEB("\n\n");
        return rep[n];
    }

    void solve() {
        cin >> n >> queries;
        cin >> s;

        ll initial_result = run_dp();
        cout << initial_result << "\n";

        while (queries--) {
            int pos;
            string letter;
            cin >> pos >> letter;
            s[pos - 1] = letter[0];

            ll query_result = run_dp();
            cout << query_result << "\n";
        }
    }
};

int main() {
    ios::sync_with_stdio(false);
    cin.tie(0);
    int z = 1;
    // cin >> z;
    while (z--) {
        Case().solve();
    }
}