#include <bits/stdc++.h>
using namespace std;
#define int long long
#define endl '\n'
bool check(string a, string b){
int n = a.size() - 1;
int prev = 0;
for (int i = 1; i < n; i++){
a[i] = (97 + (a[i] - 'a' + prev) % 26);
if (b[i] >= a[i]){
prev = b[i] - a[i];
}
else{
prev = b[i] - 'a' + 'z' - a[i] + 1;
}
a[i] = b[i];
}
a[n] = (97 + (a[n] - 'a' + prev) % 26);
return (a == b);
}
void solve(){
int n, q; cin >> n >> q;
string s, t; cin >> s >> t;
s = "." + s;
t = "." + t;
cout << (check(s, t) ? "da" : "ne") << endl;
for (int Q = 1; Q <= q; Q++){
int idx; char C;
cin >> idx >> C;
s[idx] = C;
cout << (check(s, t) ? "da" : "ne") << endl;
}
}
signed main(){
ios::sync_with_stdio();
cin.tie(0); cout.tie(0);
int tc = 1;
// cin >> tc;
for (int i = 1; i <= tc; i++){
solve();
}
}
