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#include<bits/stdc++.h>
using namespace std;
using LL=long long;
#define FOR(i,l,r)for(int i=(l);i<=(r);++i)
#define REP(i,n)FOR(i,0,(n)-1)
#define ssize(x)int(x.size())
#ifdef DEBUG
auto operator<<(auto&o,auto x)->decltype(x.end(),o);
auto&operator<<(auto&o,pair<auto,auto>p){return o<<"("<<p.first<<", "<<p.second<<")";}
auto&operator<<(auto&o,tuple<auto,auto,auto>t){return o<<"("<<get<0>(t)<<", "<<get<1>(t)<<", "<<get<2>(t)<<")";}
auto&operator<<(auto&o,tuple<auto,auto,auto,auto>t){return o<<"("<<get<0>(t)<<", "<<get<1>(t)<<", "<<get<2>(t)<<", "<<get<3>(t)<<")";}
auto operator<<(auto&o,auto x)->decltype(x.end(),o){o<<"{";int i=0;for(auto e:x)o<<","+!i++<<e;return o<<"}";}
#define debug(X...)cerr<<"["#X"]: ",[](auto...$){((cerr<<$<<"; "),...)<<endl;}(X)
#else
#define debug(...){}
#endif

constexpr LL mod = 998'244'353;
LL add(LL a, LL b) {
	a += b;
	return a >= mod ? a - mod : a;
}
LL sub(LL a, LL b) {
	return add(a, mod - b);
}
LL mul(LL a, LL b) {
	return a * b % mod;
}

constexpr int A = 6;
using TM = array<array<LL, A + 1>, A + 1>;

void clear_matrix(TM& m) {
	REP(i, A + 1) {
		REP(j, A + 1) {
			m[i][j] = 0;
		}
	}
}

TM operator*(TM a, TM b) {
	TM c;
	clear_matrix(c);
	REP(k, A + 1) {
		REP(i, A + 1) {
			REP(j, A + 1) {
				c[i][j] += a[i][k] * b[k][j];
			}
		}
	}
	REP(i, A + 1) {
		REP(j, A + 1) {
			c[i][j] %= mod;
		}
	}
	return c;
}
TM id() {
	TM ret;
	REP(i, A + 1)
		REP(j, A + 1)
			ret[i][j] = i == j;
	return ret;
}

struct Tree {
	int sz = 1;
	vector<TM> tree;
	Tree(vector<TM> v) {
		const int n = ssize(v);
		while (sz < n)
			sz *= 2;
		tree.resize(2 * sz);
		REP(i, n)
			tree[sz + i] = v[i];
		FOR(i, n, sz - 1)
			tree[sz + i] = id();
		for (int i = sz - 1; i >= 1; --i)
			tree[i] = tree[i * 2] * tree[i * 2 + 1];
	}
	void update(int w, TM m) {
		w += sz;
		if (tree[w] == m)
			return;
		tree[w] = m;
		while (w /= 2) {
			const auto new_m = tree[w * 2] * tree[w * 2 + 1];
			if (tree[w] == new_m)
				return;
			tree[w] = new_m;
		}
	}
	TM query() {
		return tree[1];
	}
};

vector<TM> tm_matrices(A);
constexpr int N = 1 << A;
vector um_matrices(A, vector<TM>(N));

void solve() {
	int n, q;
	cin >> n >> q;
	vector<int> v(n);
	REP(i, n) {
		char x;
		cin >> x;
		v[i] = int(x - 'a');
	}

	vector<TM> initial_tm(n);
	REP(i, n)
		initial_tm[i] = tm_matrices[v[i]];

	Tree tm_tree(initial_tm);

	vector<set<int>> s(A);
	REP(i, A)
		s[i].emplace(-1);
	REP(i, n)
		s[v[i]].emplace(i);

	auto get_mask_for_position = [&](int pos) -> int {
		const int letter = v[pos];
		auto it = s[letter].find(pos);
		int left = -1;
		if (it != s[letter].begin()) {
			left = *prev(it);
		}
		int mask = 0;
		REP(i, A) {
			if (i == letter)
				continue;
			auto h = s[i].upper_bound(left);
			if (h != s[i].end() and *h < pos) {
				mask |= (1 << i);
			}
		}
		return mask;
	};
	auto get_um_for_position = [&](int pos) -> TM {
		const auto mask = get_mask_for_position(pos);
		const int letter = v[pos];
		auto ret = um_matrices[letter][mask];
		if (prev(s[letter].find(pos)) == s[letter].begin()) {
			ret[letter][A] = 1;
			ret[letter][letter] = 0;
		}
		return ret;
	};

	vector<TM> initial_um(n);
	REP(i, n)
		initial_um[i] = get_um_for_position(i);
	reverse(initial_um.begin(), initial_um.end());

	Tree um_tree(initial_um);

	auto get_total = [&]() {
		auto m = tm_tree.query();
		return sub(m[A][A], 1);
	};
	auto get_unique = [&]() {
		auto m = um_tree.query();
		int ret = 0;
		REP(i, A)
			ret = int(add(ret, m[i][A]));
		return ret;
	};
	auto get_answer = [&]() {
		return sub(get_total(), get_unique());
	};

	cout << get_answer() << '\n';
	REP(i, q) {
		int p;
		char x;
		cin >> p >> x;
		--p;
		s[v[p]].erase(p);
		v[p] = int(x - 'a');
		s[v[p]].emplace(p);
		tm_tree.update(p, tm_matrices[v[p]]);
		um_tree.update(n - 1 - p, get_um_for_position(p));
		REP(j, A) {
			auto it = s[j].upper_bound(p);
			if (it == s[j].end())
				continue;
			const int h = *it;
			um_tree.update(n - 1 - h, get_um_for_position(h));
		}
		cout << get_answer() << '\n';
	}
}

int main() {
	cin.tie(0)->sync_with_stdio(0);

	REP(i, A) {
		tm_matrices[i] = id();
		tm_matrices[i][i][i] = 0;
		tm_matrices[i][i][A] = 1;
		tm_matrices[i][A][A] = 2;
		tm_matrices[i][A][i] = mod - 1;
	}
	REP(i, A) {
		REP(mask, N) {
			if ((mask >> i) & 1)
				continue;
			um_matrices[i][mask] = id();
			REP(j, A) {
				if (i == j)
					continue;
				um_matrices[i][mask][i][j] = (mask >> j) & 1;
			}
		}
	}

	solve();
}