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#include <bits/stdc++.h>

using namespace std;

#define st first
#define nd second
#define pb push_back
#define rep(i,a,b) for(int i = a; i <= b; i++)
#define irep(i,a,b) for(int i = a; i >= b; i--)
typedef long long ll;
typedef long double ld;
//typedef __int128 int128;
typedef vector<int> vi;
typedef pair<int,int> pi; 
typedef pair<double,double> pd;
typedef pair<ll,ll> pl;

const ll mod = 998'244'353;
const int max_n = 5e4+7;

int arr[max_n];
ll dp[max_n];
ll dp2[max_n][2];
ll last[max_n];
map<string,int> m;

int main(){

    ios::sync_with_stdio(0);
    cin.tie(0);

    int n,q; cin >> n >> q;
    string s; cin >> s;

    bool check_ab = 1;
    rep(i,0,n-1) if(s[i] != 'a' && s[i] != 'b') check_ab = 0;

    if(check_ab){
        while(1){
            //cout << "nowy test\n";
            //cout << "arr: "; rep(i,1,n) cout << arr[i]; cout << '\n';
            ll p[2] = {0,0};
            rep(i,1,n){
                arr[i] = s[i-1]-'a';
                last[i] = p[arr[i]];
                p[arr[i]] = i;
                //cout << "i: " << i << " last: " << last[i] << '\n';
            }
    
            //podzial na grupy!!!
            int ile_gr = 1;
            rep(i,2,n) if(arr[i] != arr[i-1]) ile_gr++;
    
            ll sum[2] = {0,0};
            rep(i,1,n){
                dp[i] = sum[arr[i]^1]+dp[last[i]];
                if(last[i] == 0) dp[i]++;
                if(dp[i] >= mod) dp[i] -= mod;
    
                sum[arr[i]^1] = 0;
                sum[arr[i]] += dp[i]; if(sum[arr[i]] >= mod) sum[arr[i]] -= mod;
                //cout << "i: " << i << " dp: " << dp[i] << '\n';
            }
    
            ll ans = 0;
            rep(i,1,n) ans += dp[i];
    
            dp2[1][0] = 1; dp2[1][1] = 1;
            rep(i,2,ile_gr){
                dp2[i][0] = dp2[i-1][1];
                dp2[i][1] = dp2[i-1][0]+dp2[i-1][1]; if(dp2[i][1] > mod) dp2[i][1] -= mod;
            }
            ans = (ans-dp2[ile_gr][0]-dp2[ile_gr][1]+2*mod)%mod;
            if(ile_gr == 1) ans++; if(ans >= mod) ans -= mod; //wtedy check na 1 grupe!!!
            cout << ans << '\n';
    
            if(q == 0) break;
            q--; 
            int a; char c;
            cin >> a >> c; s[a-1] = c;
        }
    }

    else{
        while(1){
            rep(mask,0,(1<<n)-1){
                string x;
                rep(i,0,n-1) if(mask&(1<<i)) x += s[i];
                m[x]++;
            }
            int ans = 0;
            for(auto x:m) if(x.nd > 1) ans++;
            cout << ans << '\n';
    
            if(q == 0) break;
            q--;
            int a; char c;
            cin >> a >> c; s[a-1] = c;
            m.clear();
        }
    }
    

    return 0;
}

//g++ -O3 -static -Wall .cpp -std=c++17