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#ifdef DEBUG
#define _GLIBCXX_DEBUG
#endif
//#pragma GCC optimize("O3")
#include<bits/stdc++.h>
using namespace std;

#ifdef DEBUG
#include "lib/debug.h"
#else
#define debug(...) 228
#endif

#define pb push_back

typedef long long ll;
typedef long double ld;
const int mod = 998'244'353;
int sum(int a, int b) {
    int s = a + b;
    if (s >= mod) s -= mod;
    return s;
}
int sub(int a, int b) {
    int s = a - b;
    if (s < 0) s += mod;
    return s;
}
int mult(int a, int b) {
    return (1LL * a * b) % mod;
}
int n, q;
const int maxN = 5e4 + 10;
int val[4 * maxN];
int fi[4 * maxN][6];
int lst[4 * maxN][6];
int dp[4 * maxN][6][6];
int all[4 * maxN][7][7];
int calc() {
    int ans = sub(all[1][6][6], 1);
    for (int i = 0; i < 6; i++) {
        for (int j = 0; j < 6; j++) {
            ans = sub(ans, dp[1][i][j]);
        }
    }
    return ans;
}
const int INF = 1e9;
void merge(int v) {
    for (int x = 0; x < 6; x++) {
        fi[v][x] = min(fi[2 * v][x], fi[2 * v + 1][x]);
        lst[v][x] = max(lst[2 * v][x], lst[2 * v + 1][x]);
        for (int y = 0; y < 6; y++) {
            dp[v][x][y] = 0;
        }
    }
    for (int x = 0; x < 7; x++) {
        for (int y = 0; y < 7; y++) {
            all[v][x][y] = 0;
            for (int z = 0; z < 7; z++) {
                all[v][x][y] = sum(all[v][x][y], mult(all[2 * v][x][z], all[2 * v + 1][z][y]));
            }
        }
    }
    for (int b = 0; b < 6; b++) {
        if (lst[2 * v][b] == -1) continue;
        for (int c = 0; c < 6; c++) {
            if (fi[2 * v + 1][c] == INF) continue;
            if (fi[2 * v + 1][b] < fi[2 * v + 1][c]) continue;
            if (lst[2 * v][c] > lst[2 * v][b]) continue;
            for (int a = 0; a < 6; a++) {
                for (int d = 0; d < 6; d++) {
                    dp[v][a][d] = sum(dp[v][a][d], mult(dp[2 * v][a][b], dp[2 * v + 1][c][d]));
                }
            }
        }
    }
    for (int a = 0; a < 6; a++) {
        for (int b = 0; b < 6; b++) {
            if (lst[2 * v + 1][b] == -1) {
                dp[v][a][b] = sum(dp[v][a][b], dp[2 * v][a][b]);
            }
            if (fi[2 * v][a] == INF) {
                dp[v][a][b] = sum(dp[v][a][b], dp[2 * v + 1][a][b]);
            }
        }
    }

}
void build(int v, int tl, int tr) {
    if (tl == tr) {
        for (int z = 0; z < 6; z++) {
            fi[v][z] = INF;
            lst[v][z] = -1;
            for (int t = 0; t < 6; t++) {
                dp[v][z][t] = 0;
            }
        }
        fi[v][val[tl]] = tl;
        lst[v][val[tl]] = tl;
        dp[v][val[tl]][val[tl]] = 1;
        for (int x = 0; x < 7; x++) {
            for (int y = 0; y < 7; y++) {
                all[v][x][y] = (x == y);
            }
        }
        all[v][6][6] = 2;
        all[v][val[tl]][val[tl]] = 0;
        all[v][6][val[tl]] = 1;
        all[v][val[tl]][6] = mod - 1;
        return;
    }
    int tm = (tl + tr) / 2;
    build(2 * v, tl, tm);
    build(2 * v + 1, tm + 1, tr);
    merge(v);
}
void upd(int v, int tl, int tr, int pos) {
    if (tl == tr) {
        for (int z = 0; z < 6; z++) {
            fi[v][z] = INF;
            lst[v][z] = -1;
            for (int t = 0; t < 6; t++) {
                dp[v][z][t] = 0;
            }
        }
        fi[v][val[tl]] = tl;
        lst[v][val[tl]] = tl;
        dp[v][val[tl]][val[tl]] = 1;
        for (int x = 0; x < 7; x++) {
            for (int y = 0; y < 7; y++) {
                all[v][x][y] = (x == y);
            }
        }
        all[v][6][6] = 2;
        all[v][val[tl]][val[tl]] = 0;
        all[v][6][val[tl]] = 1;
        all[v][val[tl]][6] = mod - 1;
        return;
    }
    int tm = (tl + tr) / 2;
    if (pos <= tm) upd(2 * v, tl, tm, pos);
    else upd(2 * v + 1, tm + 1, tr, pos);
    merge(v);
}
int main() {
    ios_base::sync_with_stdio(false);
    cin.tie(nullptr);
    auto start = std::chrono::high_resolution_clock::now();
#ifdef DEBUG
    freopen("input.txt", "r", stdin);
#endif
    cin >> n >> q;
    for (int i = 0; i < n; i++) {
        char c;
        cin >> c;
        val[i] = c - 'a';
    }
    build(1, 0, n - 1);
    cout << calc() << '\n';
    while (q--) {
        int pos;
        char c;
        cin >> pos;
        cin >> c;
        --pos;
        val[pos] = c - 'a';
        upd(1, 0, n - 1, pos);
        cout << calc() << '\n';
    }
    auto end = std::chrono::high_resolution_clock::now();
    std::cerr << "Execution Time: "
              << std::chrono::duration_cast<std::chrono::milliseconds>(end - start).count()
              << " ms" << std::endl;
    return 0;
}