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#include <bits/stdc++.h>

using namespace std;
typedef long long ll;
#define rep(i, n) for (int i = 0; i < (n); i++)
#define pb push_back
#define st first
#define nd second
const ll MOD = 998244353;
const int MAXN = 5e4 + 7;
int n, q;
string s;
ll dp[MAXN];

ll policzjed() {
    ll pom[7][6];
    rep(i, 6) {
        rep(j, 6) {
            pom[i][j] = 0ll;
        }
    }
    rep(j, 6) {
        pom[6][j] = 1ll;
    }
    rep(i, n) {
        int c = s[i] - 'a';
        ll suma = 0;
        rep(x, 7) {
            suma += pom[x][c];
            suma %= MOD;
            pom[x][c] = 0ll;
        }
        // cout << "c = " << c << " s = " << s << '\n';
        rep(y, 6) {
            pom[c][y] = suma;
        }
    }
    ll ile = 0;
    rep(i, 6) {
        ile += pom[i][i];
        ile %= MOD;
    }
    return ile;
}

ll policzall() {
    ll last[6];
    rep(c, 6) {
        last[c] = 0;
    }   
    rep(i, n + 1) {
        dp[i] = 0ll;
    }
    dp[0] = 1ll;
    rep(i, n) {
        int c = s[i] - 'a';
        dp[i + 1] = 2 * dp[i] - last[c];
        dp[i + 1] += (3 * MOD);
        dp[i + 1] %= MOD;
        last[c] = dp[i];
    }
    // cout << dp[n] << '\n';
    return (dp[n] - 1);
}

ll policz() {
    ll ans = policzall() - policzjed();
    ans += MOD;
    ans %= MOD;
    return ans;
}

int main() {
    ios_base::sync_with_stdio(0); cin.tie(0); cout.tie(0);
    cin >> n >> q;
    cin >> s;
    cout << policz() << '\n';
    while (q--) {
        int x;
        cin >> x;
        x--;
        char c;
        cin >> c;
        s[x] = c;
        cout << policz() << '\n';
    }
    return 0;
}