B. William the Vigilant.cpp

#include<bits/stdc++.h>
using namespace std;
#define int long long
#define mod 1000000007
#define Time cerr << "time taken : " << (float)clock() / CLOCKS_PER_SEC << " secs" << endl;
#define pb push_back
#define mp make_pair
#define line cout << endl;
#define ff first
#define ss second
#define vi vector<int>
#define no cout << "NO" << endl;
#define yes cout << "YES" << endl;
#define printv(v)                      \
  for (int i = 0; i < (v.size()); i++) \
  {                                    \
    cout << v[i] << " ";               \
  }                                    \
  line;
#define onesbits(x) __builtin_popcountll(x)
#define zerobits(x) __builtin_ctzll(x)
#define sp(x, y) fixed << setprecision(y) << x
#define w(x) \
  int x;     \
  cin >> x;  \
  while (x--)
#define tk(x) \
  int x;      \
  cin >> x;
#define fast ios_base::sync_with_stdio(false), cin.tie(nullptr), cout.tie(nullptr);
#ifndef ONLINE_JUDGE
#define debug(x)     \
  cerr << #x << " "; \
  _print(x);         \
  cerr << endl;
#else
#define debug(x)
#endif
template <class T>
void _print(T t)
{
  cerr << t;
}
template <class T, class V>
void _print(pair<T, V> p)
{
  cerr << "{";
  _print(p.ff);
  cerr << ",";
  _print(p.ss);
  cerr << "}";
}
template <class T>
void _print(vector<T> v)
{
  cerr << "[ ";
  for (T i : v)
  {
    _print(i);
    cerr << " ";
  }
  cerr << "]";
}
template <class T>
void _print(vector<vector<T>> v) {
  cerr << "[\n";
  for (int l = 0; l < v.size(); l++)
  {
    {
      for (int k = 0; k < v[l].size(); k++)
        cerr << v[l][k] << " ";
    }
    cerr << "\n";
  }
  cerr << "]";
}
template <class T, class V>
void _print(map<T, V> v)
{
  cerr << "[ ";
  for (auto i : v)
  {
    _print(i);
    cerr << " ";
  }
  cerr << "]";
}
template <class T>
void _print(set<T> v)
{
  cerr << "[ ";
  for (T i : v)
  {
    _print(i);
    cerr << " ";
  }
  cerr << "]";
}

const long long inf = 1e18;
const int MOD = 998244353;
const int MAX = 1e6;
const int N = 200010;

bool isValid(string s) {
  int len = s.size();
  for (int i = 0; i < len / 2; i++) {
    if (s[i] != s[len - 1 - i])
      return false;
  }
  return true;
}

bool good (int x) {
  int t, n, a[N];
  for (int i = 1, j = n; i <= j; ++i, --j) {
    if (a[i] == a[j]) continue;
    if (a[i] != x and a[j] != x) return 0;
    if (a[i] == x) ++j; else --i;
  } return 1;
}

int32_t main() {
    fast
  //   int t;
  //   cin >> t;
  // while(t-->0) {

    int n, q;
    cin>>n>>q;
    string s;
    cin>>s;
    int cnt=0;
    for(int i=0;i<n;i++)
    {
    	if(s[i]=='a')
    	{
    		if(i<=n-3 && s[i+1]=='b' && s[i+2]=='c')
    			cnt++;
    	}
    }
    while(q--)
    {
    	int pos;
    	cin>>pos;
    	char c;
    	cin>>c;
    	pos--;
    	if(s[pos]==c)
    	{
    		cout<<cnt<<endl;
    	}
    	else
    	{
    		int fl=0;
    		if(s[pos]=='a')
    		{
    			if(pos<=n-3 && s[pos+1]=='b' && s[pos+2]=='c')
    			{
    				fl=1;
    			}
    		}
    		else if(s[pos]=='b')
    		{
    			if(pos<=n-2 && pos>=1 && s[pos-1]=='a' && s[pos+1]=='c')
    			{
    				fl=1;
    			}
    		}
    		else
    		{
    			if(pos>=2 && s[pos-1]=='b' && s[pos-2]=='a')
    			{
    				fl=1;
    			}
    		}
    		if(fl==1) {
    			cnt--;
    		}
    		// else
    		// {
    			int fl1=0;
    			if(c=='a')
    			{
    				if(pos<=n-3 && s[pos+1]=='b' && s[pos+2]=='c')
	    			{
	    				fl1=1;
	    			}
    			}
    			else if(c=='b')
    			{
    				if(pos<=n-2 && pos>=1 && s[pos-1]=='a' && s[pos+1]=='c')
	    			{
	    				fl1=1;
	    			}
    			}
    			else
    			{
    				if(pos>=2 && s[pos-1]=='b' && s[pos-2]=='a')
	    			{
	    				fl1=1;
	    			}
    			}
    			s[pos]=c;
    			if(fl1==1)
    			{
    				cnt++;
    			}
    		// }
    		cout<<cnt<<endl;
    	}
    }
    
    
  // }

  return 0;
}