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#include<bits/stdc++.h>
#define FOR(i,a,b) for(int i=a;i<(int)b;++i)
#define FORD(i,a,b) for(int i=a;i>=(int)b;--i)
#define PB push_back
#define EB emplace_back
#define FI first
#define SE second
#define umap unordered_map
#define uset unordered_set
#define vi vector<int>
#define vvi vector<vi>
#define vll vector<ll>
#define vvll vector<vll>
#define vpii vector<pii>
#define pii pair<int, int>
#define pll pair<ll, ll>
#define ALL(X) (X).begin(),(X).end()
#ifndef DEBUG
#define endl (char)10
#endif
using namespace std;
using ll = long long;
using ld = long double;

template <class T>
istream& operator>> (istream& is, vector<T>& vec){
    FOR(i,0,vec.size()) is >> vec[i];
    return is;
}
template <class T>
ostream& operator<< (ostream& os, vector<T>& vec){
    for(auto& t : vec) os << t << " ";
    return os;
}
template<class T, class U>
ostream& operator<< (ostream& os, const pair<T, U>& p){
    os << p.FI << " " << p.SE;
    return os;
}
template<class T, class U>
istream& operator>> (istream& is, pair<T, U>& p){
    is >> p.FI >> p.SE;
    return is;
}

const int M = 998'244'353;

// TODO: take & and change inplace
constexpr int add(int a, int b) {
    int ans = a + b;
    if (ans >= M) ans -= M;
    return ans;
}

int jedno_wyst(string& s) {
    vi score(6, 1);
    vi kiedy(6, -1);
    FOR(i,0,s.size()) {
        FOR(j,0,6) if(kiedy[j] > kiedy[s[i]]) score[s[i]] = add(score[s[i]], score[j]);
        kiedy[s[i]] = i;
    }
    int ans = 1;
    FOR(i,0,6) if(kiedy[i] != -1) ans = add(ans, score[i]);
    return ans;
}

int co_najmniej_jedno_wyst(string& s) {
    vi score(6, 0);
    int ans = 1;
    FOR(i,0,s.size()) {
        int ns = ans;
        ans = add(ans, ans);
        ans = (ans >= score[s[i]] ? ans - score[s[i]] : add(ans, M - score[s[i]]));
        score[s[i]] = ns;
    }
    return ans;
}

int solve(string& s) {
    int a = jedno_wyst(s);
    int b = co_najmniej_jedno_wyst(s);
    if (b >= a) return b - a;
    return add(b, M - a);
}

int main () {
    ios_base::sync_with_stdio(false);
    cin.tie(0);
    int n, q;
    string s;
    cin >> n >> q >> s;
    FOR(i,0,n) s[i] -= 'a';
    int prevans = solve(s);
    cout << prevans << endl;
    while(q--){
        int i;
        char c;
        cin >> i >> c;
        c -= 'a';
        i--;
        if (s[i] != c) {
            s[i] = c;
            prevans = solve(s);
        }
        cout << prevans << endl;
    }
}