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#include <bits/stdc++.h>
using namespace std;
#define st first
#define nd second
#define pb push_back
#define all(x) (x).begin(), (x).end()
#define BOOST ios_base::sync_with_stdio(0), cin.tie(0)
typedef long long ll;
typedef long double ld;
typedef pair<int, int> ii;

const int N = 5e4 + 5, M = 7, mod = 998244353;
int ms = 7;
set<int> s[M];

using Matrix = vector<vector<int>>;
Matrix makeId(){
	Matrix x(ms, vector<int>(ms));
	for(int i=0; i<ms; i++) x[i][i] = 1;
	return x;
}
Matrix Id;
vector<int> base;
// ostream& operator<<(ostream& os, const Matrix& matrix) {
//     for (const auto& row : matrix) {
//         os << "[";
//         for (size_t i = 0; i < row.size(); ++i) {
//             os << row[i];
//             if (i < row.size() - 1) {
//                 os << ", ";
//             }
//         }
//         os << "]" << endl;
//     }
//     return os;
// }

inline int add(int a, int b){
	a += b;
	if(a >= mod) a -= mod;
	return a;
}

inline int sub(int a, int b){
	return (a-b+mod) %mod;
}

// int cnt = 0;
inline int mul(int a, int b){
	// cnt++;
	return (ll)a*b %mod;
}

Matrix operator*(const Matrix& a, const Matrix& b) {
	if(a.empty() || b.empty()) return {{}};
	Matrix c(ms, vector<int>(ms));
	c[0][0] = 1;
	for (int i = 1; i < ms; i++) {
		for (int j = 0; j < ms; j++) {
			for (int k = 0; k < ms; k++) {
				c[i][j] = add(c[i][j], mul(a[i][k], b[k][j]));
			}
		}
	}
	return c;
}

vector<int> operator*(const Matrix& a, const vector<int>& b) {
	vector<int> c(ms);
	for (int i = 0; i < ms; i++) {
		for (int j = 0; j < ms; j++) {
			c[i] = add(c[i], mul(a[i][j], b[j]));
		}
	}
	return c;
}

struct tree{
	int pot;
	vector<Matrix> t;
	tree(int n){
		pot = 1;
		while(pot <= n) pot *= 2;
		t = vector<Matrix>(pot * 2);
		for(int i=0; i<pot*2; i++){
			t[i] = Id;
		}
	}
	void build(){
		for(int i=pot-1; i>=1; i--){
			t[i] = t[i*2+1] * t[i*2];
		}
	}
	void modify(int x, Matrix a){
		t[x += pot] = a;
		for(x/=2; x; x/=2){
			t[x] = t[x*2+1] * t[x*2];
		}
	}
	void maybe(int x, Matrix a){
		if(a != t[x+pot]) modify(x, a);
	}
};

int right(int i, int x){
	auto it = s[x].upper_bound(i);
	if(it == s[x].end()) return -1;
	return *it;
}

int left(int i, int x){
	auto it = s[x].lower_bound(i);
	if(it == s[x].begin()) return -1;
	return *--it;
}

int t[N];

int main(){
	BOOST;
	
	int n, q;
	cin >> n >> q;
	string dat; cin >> dat;
	vector<pair<int, char>> query(q);
	
	bool ab = 1;
	s[0].insert(0);
	for(int i=1; i<=n; i++){
		t[i] = dat[i-1] - 'a' + 1;
		s[t[i]].insert(i);
		if(t[i] != 1 && t[i] != 2) ab = 0;
	}
	for(int i=0; i<q; i++){
		int a;
		char b;
		cin >> a >> b;
		query[i] = {a, b};
		if(b != 'a' && b != 'b') ab = 0;
	}
	if(ab){
		ms = 3;
		// cout << "ab only!\n";
		// exit(0);
	}
	
	Id = makeId();
	base = Id[0];
	tree two(n), one(n);

	auto m1 = [&](int i) -> Matrix {
		Matrix x = Id;
		for(int j=0; j<ms; j++){
			x[t[i]][j] = 1;
		}
		return x;
	};

	auto m2 = [&](int i) -> Matrix {
		Matrix x = Id;
		for(int j=0; j<ms; j++){
			if(left(i, t[i]) <= left(i, j)){
				x[t[i]][j] = 1;
			}
		}
		return x;
	};
	auto res = [&]() -> void {
		int two_res = 0, one_res = 0;
		auto a = two.t[1]*base; // t[1]?
		auto b = one.t[1]*base;
		for(int i=1; i<ms; i++){
			two_res = add(two_res, a[i]);
			one_res = add(one_res, b[i]);
		}
		cout << sub(two_res, one_res) << "\n";
	};

	for(int i=1; i<=n; i++){
		two.t[i+two.pot] = m1(i);
		one.t[i+one.pot] = m2(i);
	}
	two.build();
	one.build();
	res();
	
	for(auto it : query){
		int i = it.st;
		int c = it.nd;
		s[t[i]].erase(i);
		t[i] = c - 'a' + 1;
		s[t[i]].insert(i);

		two.modify(i, m1(i));
		one.modify(i, m2(i));

		for(int j=0; j<ms; j++){
			int r = right(i, j);
			if(r != -1) one.maybe(r, m2(r));
		}

		res();
	}
	// printf("cnt = %d\n", cnt);
}

// precomp macierzy z 4 liter
// opt z ab