#include <bits/stdc++.h>
using namespace std;
using ll=long long;
#define F first
#define S second
#define sz(x) int(x.size())
string odg[2]={"ne", "da"};
int n, q;
string s, t, so;
int f() {
for(int i=0; i<n-1; i++) {
int d=t[i]-s[i]+26;
d%=26;
s[i]-='a';
s[i]+=d;
s[i]%=26;
s[i]+='a';
s[i+1]-='a';
s[i+1]+=d;
s[i+1]%=26;
s[i+1]+='a';
}
return s==t;
}
signed main() {
ios_base::sync_with_stdio(0); cin.tie(0); cout.tie(0);
cin >> n >> q;
cin >> s >> t;
so=s;
if(q==0) {
cout << odg[f()] << '\n';
return 0;
}
cout << odg[f()] << '\n';
while(q--) {
int p;
char c;
cin >> p >> c;
so[p-1]=c;
s=so;
// cout << s << ' ' << t << '\n';
cout << odg[f()] << '\n';
}
return 0;
}
