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#include <iostream>
#include <vector>
using namespace std;

#define LL long long
#define MOD 998244353

inline LL add(LL a, LL b) { a += b; if(a >= MOD) a -= MOD; return a; }
inline LL sub(LL a, LL b) { a -= b; if(a < 0) a += MOD; return a; }
inline LL mul(LL a, LL b) { return (a % MOD) * (b % MOD) % MOD; }

void compute_dp(const string &s, int n, vector<LL>& F, vector<LL>& U) {
    vector<int> last(6, 0);
    vector<LL> newContrib(6, 0);
    F[0] = 0; U[0] = 0;
    for (int i = 1; i <= n; i++){
        int c = s[i-1] - 'a';
        if(last[c] == 0) {
            F[i] = (2 * F[i-1] + 1) % MOD;

            LL addUnique = (U[i-1] + 1) % MOD;
            U[i] = (U[i-1] + addUnique) % MOD;
            newContrib[c] = addUnique;
        } else {
            int j = last[c];
            F[i] = (2 * F[i-1] - F[j-1] + MOD) % MOD;
            LL diff = (F[i-1] - F[j-1] + MOD) % MOD;

            U[i] = (U[i-1] + diff - newContrib[c] + MOD) % MOD;
            newContrib[c] = diff;
        }
        last[c] = i;
    }
}

int main(){
    int n, q;
    cin >> n >> q;
    string s;
    cin >> s;

    vector<LL> F(n+1, 0), U(n+1, 0);
    compute_dp(s, n, F, U);

    LL ans = (F[n] - U[n] + MOD) % MOD;
    cout << ans << "\n";

    for (int i = 0; i < q; i++){
        int pos;
        char c;
        cin >> pos >> c;
        if(s[pos-1] == c) {
            cout << ans << endl;
            continue;
        }
        s[pos-1] = c;
        compute_dp(s, n, F, U);
        ans = (F[n] - U[n] + MOD) % MOD;
        cout << ans << endl;
    }
    return 0;
}