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#include <bits/stdc++.h>
using namespace std;
#pragma GCC optimize ("Ofast")
#pragma GCC optimize ("unroll-loops")
typedef long long LL;

const LL MOD = 998244353;

LL dp[50005];
LL l[8];
LL p[8];
int n, q;
string s;

LL f(){
	dp[1]=1;
	for(int i=0; i<8; i++) l[i] = p[i] = 0;
	for(int i=2; i<n; i++){
		int x = s[i]-'a';
		dp[i] = (dp[i-1] * 2 - l[x] + MOD) % MOD;
		l[x] = dp[i-1];
	}
	int m = 0;
	for(int i=0; i<8; i++){
		if(l[i])m=i+1;
	}
	vector<pair<LL, LL>> d(m);
	
	for(int i=2; i<n; i++){
		int x = s[i]-'a';
		if(p[x] == 0){
			p[x]=i;
			d[x].first++;
		}
		LL sum = 0;
		for(int j=0; j<m; j++){
			if(d[j].second > d[x].second) sum += d[j].first; 
		}
		d[x].first = (d[x].first + sum) % MOD;
		d[x].second = i;
	}
	
	LL sum = 0;
	for(int j=0; j<m; j++) sum += d[j].first;
	
	return (dp[n-1] - sum%MOD - 1 + MOD) % MOD;
}

int main() {
	ios_base::sync_with_stdio(false);
	cin.tie(0);
	cout.tie(0);

	cin>>n>>q;
	cin>>s;
	s = ".." + s;
	n++;
	n++;
	
	cout<<f()<<"\n";
	
	while(q--){
		int id;
		char c;
		cin>>id>>c;
		s[id+1] = c;
		cout<<f()<<"\n";
	}
	
	
	
	return 0;
}