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#include <bits/stdc++.h>
using namespace std;

#ifdef DEBUG
auto &operator<<(auto &o, pair<auto, auto> p) {
    return o << "(" << p.first << ", " << p.second <<")";
}
auto operator<<(auto &o, auto x)-> decltype(x.end(), o) {
    o << "{";int i = 0;
    for(auto e : x) o << ", "+!i++<<e;
    return o <<"}";
}
#define debug(x...) cerr << "["#x"]: ",[](auto...$){((cerr<<$<<"; "),...)<<endl;}(x)
#else
#define debug(...) {}
#endif

#define int long long
#define all(x) x.begin(), x.end()
#define sz(x) (int)(x).size()
#define pb push_back
#define fi first
#define se second
typedef pair <int, int> pii;

int const mod = 1e9+123;
int const MOD = 998244353;

int solve2(string &s) {
    map <int, int> M;

    int const n = sz(s);
    for (int i=1; i<(1<<n); ++i) {
        int hsh = 0, p = 1; 
        for (int j=0; j<n; ++j) {
            if ((1<<j) & i) {
                hsh = (hsh + (p*(s[j] - '0' + 1))%mod);
                p = (p*7ll)%mod;
            }
        }
        M[hsh]++;
    }

    int ret = 0;
    for (auto &[x, y] : M) {
        if (y > 1) ret++;
    }
    return ret%MOD;
}


int solve(string &s) {
    debug("SOLVE-------", s);
    int const n = sz(s);
    vector <vector <int> > ile(n+1, vector <int>(7));
    vector <int> last(7, 0);
    vector <int> ilen(n+1);
    ilen[0] = 1;
    for (int i=1; i<=n; ++i) {
        int lt = s[i-1] - 'a';
        ilen[i] = (MOD + (2ll * ilen[i-1]) - (last[lt] > 0 ? ilen[last[lt]-1] : 0))%MOD; 
        last[lt] = i;
    }  
    debug(ilen); 

    last = vector <int> (7, 0);
    for (int i=1; i<=n; ++i) {
        int c = s[i-1] - 'a';
        // pelny prefix wystepuje raz na pewno
        // kazde slowo, ktore wystapilo raz do tamtej literki mozna przedluzyc        
        
        for (int j=0; j<6; ++j){
            if (j == c) { // ta sama literka
                ile[i][c] = (ile[i][c] + ile[i-1][c])%MOD;
            }
            else {
                ile[i][j] = ile[i-1][j];
                if (last[j] >= last[c])
                    ile[i][c] = (ile[i][c] + ile[i-1][j])%MOD;
            }
        }
        if (last[c] == 0) ile[i][c] = (ile[i][c]+1)%MOD;
        last[c] = i;
    }


    debug(sz(ile), n);
    for (int i=1; i<=n; ++i) {
        debug(i, "------------");
        debug(ile[i]);
    }


    int ret = 0;
    for (int i=0; i<6; ++i) {
        ret = (ret + ile[n][i])%MOD;
    }
    return ((2ll * MOD) - 1ll + ilen[n] - ret)%MOD;

}


void test() {
    debug("TC______________________");
    int n, q; cin>>n>>q;

    string s; cin>>s;

    cout<<solve(s)<<'\n';
    debug("asdasd");
    for (int i=0; i<q; ++i) {
        int p; char c;
        cin>>p>>c;
        s[p-1] = c;
        cout<<solve(s)<<'\n';
    }
}

signed main() {
  ios_base::sync_with_stdio(0); cin.tie(0);
  int t = 1; 
  while (t--) {
    test();
  }
}