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#include <vector>
#include <cstdio>
#include <stack>
#include <algorithm>
#include <queue>
#include <map>
#include <cmath>
#include <unordered_set>
#include <unordered_map>
#include <set>
#include <cstring>
#include <bitset>
#include <iostream>
#include <queue>
#include <iomanip>
#include <complex>

using namespace std;

#define ALL(x) x.begin(), x.end()
#define UNIQUE(c) (c).resize(unique(ALL(c)) - (c).begin())
#define FOR(i, a, b) for(int i =(a); i <=(b); ++i)
#define RE(i, n) FOR(i, 1, n)
#define RED(i, n) FORD(i, n, 1)
#define FORD(i, a, b) for(int i = (a); i >= (b); --i)
#define REP(i, n) for(int i = 0;i <(n); ++i)
#define REPD(i, n) FORD(i, n-1,0)

#define printA(a, L, R) FOR(i,L,R) cout << a[i] << (i==R?'\n':' ')
#define printV(a) printA(a,0,a.size()-1)
#define PRESENT(c, x) ((c).find(x) != (c).end())
#define CPRESENT(c, x) (find(ALL(c),x) != (c).end())
#define bit(x, i) (x&(1<<i))
#define lowbit(x) ((x)&((x)^((x)-1)))

const int fx[4][2] = {
    {0, 1},
    {1, 0},
    {0, -1},
    {-1, 0}
};
const int fxx[8][2] = {
    {0, 1},
    {0, -1},
    {1, 0},
    {-1, 0},
    {1, 1},
    {1, -1},
    {-1, 1},
    {-1, -1}
};
const int sk[8][2] = {
    {2, 1},
    {2, -1},
    {-2, -1},
    {-2, 1},
    {1, 2},
    {-1, 2},
    {1, -2},
    {-1, -2}
};

const int maxl = 6, mod = 998244353, maxn = 50012;
int n, q, uni[maxl][maxn], wyn[maxn], dup[maxl][maxn], a[maxn], po, la[maxl], ll;
set<int> poz[maxl];
string s;

void licz(int l, int r) {
    if (ll <= 1) {
        FOR(i, l, r) {
            uni[a[i]][i] = (la[a[i]] == 0) + uni[a[i]][la[a[i]]] + (la[a[i]] < la[1 - a[i]] ? uni[1 - a[i]][la[1 - a[i]]] : 0);
            if (uni[a[i]][i] >= mod) uni[a[i]][i] -= mod;
            dup[a[i]][i] = (la[a[i]] != 0) + wyn[i - 1] + (la[a[i]] > la[1 - a[i]] ? uni[1 - a[i]][la[1 - a[i]]] : 0);
            if (dup[a[i]][i] >= mod) dup[a[i]][i] -= mod;
            wyn[i] = dup[1 - a[i]][la[1 - a[i]]] + dup[a[i]][i];
            if (wyn[i] >= mod) wyn[i] -= mod;
            la[a[i]] = i;
        }
    } else {
        FOR(i, l, r) {
            uni[a[i]][i] = la[a[i]] == 0;
            dup[a[i]][i] = (la[a[i]] != 0) + wyn[i - 1];
            if (dup[a[i]][i] >= mod) dup[a[i]][i] -= mod;
            REP(li, ll + 1) {
                if (la[a[i]] <= la[li]) {
                    uni[a[i]][i] += uni[li][la[li]];
                    if (uni[a[i]][i] >= mod) uni[a[i]][i] -= mod;
                } else {
                    dup[a[i]][i] += uni[li][la[li]];
                    if (dup[a[i]][i] >= mod) dup[a[i]][i] -= mod;
                }
            }
            wyn[i] = wyn[i - 1] + dup[a[i]][i] - dup[a[i]][la[a[i]]];
            if (wyn[i] < 0) wyn[i] += mod;
            if (wyn[i] >= mod) wyn[i] -= mod;
            la[a[i]] = i;
        }
    }
}

void solve() {
    cin >> n >> q >> s;
    RE(i, n) {
        a[i] = s[i - 1] - 'a';
        poz[a[i]].insert(i);
        ll = max(a[i], ll);
    }

    licz(1, n);
    cout << wyn[n] << "\n";

    while (q--) {
        cin >> po >> s;
        auto akt = s[0] - 'a', pakt = a[po];
        if (akt != pakt) {
            ll = max(akt, ll);
            a[po] = akt;
            poz[akt].insert(po);
            poz[pakt].erase(po);
            REP(i, ll + 1) {
                auto it = poz[i].lower_bound(po);
                if (it == poz[i].begin()) {
                    la[i] = 0;
                } else {
                    la[i] = *(--it);
                }
            }
            licz(po, n);
        }
        cout << wyn[n] << "\n";
    }
}

int main() {
    ios_base::sync_with_stdio(false), cin.tie(nullptr);

    int tt = 1;
    // cin >> tt;
    while (tt--) {
        solve();
    }
    return 0;
}