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#include <bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>
#define ll long long
#define ld long double
#define ull unsigned long long
#define ff first
#define ss second
#define pii pair<int,int>
#define pll pair<long long, long long>
#define vi vector<int>
#define vl vector<long long>
#define pb push_back
#define rep(i, b) for(int i = 0; i < (b); ++i)
#define rep2(i,a,b) for(int i = a; i <= (b); ++i)
#define rep3(i,a,b,c) for(int i = a; i <= (b); i+=c)
#define count_bits(x) __builtin_popcountll((x))
#define all(x) (x).begin(),(x).end()
#define siz(x) (int)(x).size()
#define forall(it,x) for(auto& it:(x))
using namespace __gnu_pbds;
using namespace std;
typedef tree<int, null_type, less<int>, rb_tree_tag,tree_order_statistics_node_update> ordered_set;
//mt19937 mt;void random_start(){mt.seed(chrono::time_point_cast<chrono::milliseconds>(chrono::high_resolution_clock::now()).time_since_epoch().count());}
//ll los(ll a, ll b) {return a + (mt() % (b-a+1));}
const int INF = 1e9+50;
const ll INF_L = 1e18+40;
const ll MOD = 998'244'353;

ll dp1[50'002];
ll dp2[50'002];
string s;
int prev_[400];

ll count_ans()
{
    int n = siz(s)-1;
    rep2(i,1,n)
    {
        dp1[i] = 0;
        dp2[i] = 0;
    }
    rep2(c,'a','f') prev_[c] = 0;
    rep2(i,1,n)
    {
        rep2(c,'a','f')
        {
            if(prev_[c] >= prev_[s[i]])
            {
                dp1[i] += dp1[prev_[c]];
                dp1[i] %= MOD;
            }
        }
        dp2[i] = dp2[i-1]*2 - (prev_[s[i]] != 0 ? dp2[prev_[s[i]]-1] : 0) + MOD;
        dp2[i] %= MOD;
        if(prev_[s[i]] == 0)
        {
            dp1[i]++;
            dp2[i]++;
            dp1[i] %= MOD;
            dp2[i] %= MOD;
        }
        prev_[s[i]] = i;
       // cerr << dp1[i] << " " << dp2[i] << " " << s[i] << " dp\n";
    }
    ll d1 = 0;
    rep2(c,'a','f')
    {
        d1 += dp1[prev_[c]];
        d1 %= MOD;
    }
    //cerr << d1 << " " << dp2[n] << " d\n";
    return (dp2[n] - d1 + MOD) % MOD;
}

int main()
{
    ios_base::sync_with_stdio(0);cin.tie(0);cout.tie(0);
    //random_start();
    int n,q;
    cin >> n >> q;
    cin >> s;
    s = "#" + s;
    cout << count_ans() << "\n";
    rep(i,q)
    {
        int ind;
        char z;
        cin >> ind >> z;
        s[ind] = z;
        cout << count_ans() << "\n";
    }
}