#include<bits/stdc++.h>
using namespace std;
typedef long long ll;
//#include<bits/extc++.h>
//__gnu_pbds
string ans[2]={"ne","da"};
int main(){
ios_base::sync_with_stdio(0),cin.tie(0),cout.tie(0);
int n,q;cin>>n>>q;
string s;cin>>s;
string b;cin>>b;
vector<int> arr(n);
for(int i=0;i<n;i++){
arr[i] = (b[i]-s[i]);
}
vector<int> u(n);
u[n-1]=-1;
for(int j=n-2;j>=0;j--) u[j]=u[j+1]*-1;
ll sum=0;
for(int i=0;i<n;i++) sum+=u[i]*arr[i];
cout<<ans[sum%26==0]<<"\n";
for(int i=0;i<q;i++){
int p;cin>>p;
p--;
char x;cin>>x;
ll og = u[p]*arr[p];
s[p]=x;
arr[p] = b[p]-s[p];
sum-=og;
sum+=u[p]*arr[p];
cout<<ans[sum%26==0]<<"\n";
}
return 0;
}
