import sys
input=lambda:sys.stdin.readline().rstrip()
N,Q=map(int,input().split())
comp=['a','b','c']
S=list(input())
ans=sum([S[i:i+3]==comp for i in range(N-2)])
for i in range(Q):
temp=0
q=input().split()
ind=int(q[0])-1
for j in range(max(ind-2,0),min(ind+1,N-2)):
ans-=(S[j:j+3]==comp)
S[ind]=q[1]
for j in range(max(ind-2,0),min(ind+1,N-2)):
ans+=(S[j:j+3]==comp)
print(ans)#include<bits/stdc++.h>
using namespace std;
int main(){
int n,q;
cin>>n>>q;
string s="";
cin>>s;int ans=0;
if(s.size()>2){
for(int i=1;i<n-1;i++){
if(s[i]=='b'&&s[i-1]=='a'&&s[i+1]=='c'){
ans++;
}
}
}
while(q--){
int pos;char sc;
cin>>pos>>sc;
if(s[pos-1]!=sc){
if(pos-2>=0&&pos<n&&s[pos-1]=='b'&&s[pos-1-1]=='a'&&s[pos-1+1]=='c'){
ans--;
}else if(pos-1>=0&&pos+1<n&&s[pos-1]=='a'&&s[pos]=='b'&&s[pos+1]=='c'){
ans--;
}else if(pos-3>=0&&pos-1<n&&s[pos-1]=='c'&&s[pos-1-1]=='b'&&s[pos-3]=='a'){
ans--;
}
if(pos>=0&&pos+1<n&&sc=='a'&&s[pos]=='b'&&s[pos+1]=='c'){
ans++;
}else if(pos-2>=0&&pos<n&&sc=='b'&&s[pos-1-1]=='a'&&s[pos]=='c'){
ans++;
}else if(pos-3>=0&&pos-2<n&&sc=='c'&&s[pos-2]=='b'&&s[pos-3]=='a'){
ans++;
}
s[pos-1]=sc;
}
cout<<ans<<endl;
}
// another approach not came into my mind
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