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#include <bits/stdc++.h>

using namespace std;
using LL = long long;
#define FOR(i, l, r) for(int i = (l); i <= (r); ++i)
#define REP(i, n) FOR(i, 0, (n) - 1)
#define ssize(x) int(x.size())

template<class A, class B> auto &operator<<(ostream &o, pair<A, B> p) {
    return o << '(' << p.first << ", " << p.second << ')';
}

template<class T> auto operator<<(ostream &o, T x) -> decltype(x.end(), o) {
    o << '{'; int i = 0; for (auto e : x) o << (", ")+2*!i++ << e;
    return o << '}';
}

#ifdef DEBUG
#define debug(x...) cerr << "[" #x "]: ", [](auto... $) {((cerr << $ << "; "), ...); }(x), cerr << '\n';
#else
#define debug(...) {}
#endif


constexpr int MAXN = 50007;
constexpr LL mod = 998'244'353;


int n;
int a[MAXN];
LL dp[MAXN][6];
LL dp_uniq[MAXN][6];
int prev_occ[MAXN][6];


void fill_dp(int idx) {
    FOR(i, idx, n) {
        dp[i][a[i]] = 1;
        REP(j, 6) {
            if (a[i] != j)
                dp[i][j] = dp[i - 1][j];
            dp[i][a[i]] += dp[i - 1][j];
        }
        dp[i][a[i]] %= mod;
    }
}

void fill_dp_uniq(int idx) {
    FOR(i, idx, n) {
        REP(j, 6) {
            if (a[i] != j)
                dp_uniq[i][j] = dp_uniq[i - 1][j];
            prev_occ[i][j] = prev_occ[i - 1][j];
        }
        if (i != 1)
            prev_occ[i][a[i - 1]] = i - 1;

        dp_uniq[i][a[i]] = 0;
        REP(j, 6) {
            if (prev_occ[i][a[i]] <= prev_occ[i][j])
                dp_uniq[i][a[i]] += dp_uniq[prev_occ[i][j]][j];
        }
        if (prev_occ[i][a[i]] == 0)
            dp_uniq[i][a[i]]++;
        dp_uniq[i][a[i]] %= mod;
    }
}


void calculate_answer(int idx) {
    fill_dp(idx);
    fill_dp_uniq(idx);

    LL ans = 0;
    REP(i, 6)
        ans += dp[n][i] - dp_uniq[n][i] + mod;
    
    cout << ans % mod << '\n';
}


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

    int q;
    string s;
    cin >> n >> q >> s;
    REP(i, n)
        a[i + 1] = s[i] - 'a';

    calculate_answer(1);

    while (q--) {
        int idx;
        char ch;
        cin >> idx >> ch;
        a[idx] = ch - 'a';

        calculate_answer(idx);
    }

    return 0;
}