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#include <bits/stdc++.h>
using namespace std;
#define FOR(i,l,r) for(int i = (l); i <= (r); i++)
#define FORD(i,l,r) for(int i = (l); i >= (r); i--)
using num = double;
using ind = long long;
struct letter{
    ind pos=-1;
    ind wyn=0;
};
int n;
char t[50'001];
ind subsequences()
{
    vector<ind> last(6, -1);
    ind v[n + 1];
    v[0] = 1;
    FOR(i,1,n){
        v[i] = 2*v[i-1];
        if(last[t[i-1]] != -1){
            v[i] = v[i] - v[last[t[i-1]]];
        }
        if(v[i] < 0) {
            v[i] += (LONG_LONG_MAX/998244353)*998244353;
            if(v[i] < 0) {
                v[i] += (LONG_LONG_MAX/998244353)*998244353;
            }
            v[i] = v[i] % 998244353;
        }
        else {v[i] = v[i] % 998244353;}
        last[t[i-1]] = (i-1);
    }
    return v[n]-1;
}
void solve(){
    letter wyns[6];
    wyns[0].pos=-1;
    wyns[1].pos=-1;
    wyns[2].pos=-1;
    wyns[3].pos=-1;
    wyns[4].pos=-1;
    wyns[5].pos=-1;
    wyns[0].wyn=0;
    wyns[1].wyn=0;
    wyns[2].wyn=0;
    wyns[3].wyn=0;
    wyns[4].wyn=0;
    wyns[5].wyn=0;
    FOR(i,0,n-1){
        char c = t[i];
        if(wyns[c].pos==-1){wyns[c].wyn=1;}
        ind newwyn=0;
        FOR(i,0,5){
            letter let = wyns[i];
            if(let.pos >= wyns[c].pos) newwyn += let.wyn;
        }
        wyns[c].pos = i;
        if(newwyn < 0) {
            newwyn += (LONG_LONG_MAX/998244353)*998244353;
            if(newwyn < 0) {
                newwyn += (LONG_LONG_MAX/998244353)*998244353;
            }
            newwyn = newwyn % 998244353;
        }
        else {newwyn = newwyn % 998244353;}
        wyns[c].wyn = newwyn;
    }
    ind uniq = 0;
    for(letter let : wyns){
        uniq += let.wyn;
    }
    if(uniq < 0) {
        uniq += (LONG_LONG_MAX/998244353)*998244353;
        if(uniq < 0) {
            uniq += (LONG_LONG_MAX/998244353)*998244353;
        }
        uniq = uniq % 998244353;
    }
    else {uniq = uniq % 998244353;}
    ind wyn2 = subsequences()-uniq;
    if(wyn2 < 0) {
        wyn2 += (LONG_LONG_MAX/998244353)*998244353;
        if(wyn2 < 0) {
            wyn2 += (LONG_LONG_MAX/998244353)*998244353;
        }
        wyn2 = wyn2 % 998244353;
    }
    else {wyn2 = wyn2 % 998244353;}
    cout << wyn2 << '\n';
}
int main(){
    ios_base::sync_with_stdio(0);
    cin.tie(0);
    int q;
    cin >> n >> q;
    string s;
    cin >> s;
    FOR(i,1,s.size()){
        t[i-1]=s[i-1]-'a';
    }
    solve();
    while(q--){
        ind p;
        char c;
        cin >> p >> c;
        t[p-1]=c-'a';
        solve();
    }
}