#include <bits/stdc++.h>
#define int long long
#define fi first
#define se second
#define sz(a) (int)((a).size())
#define all(a) (a).begin(), (a).end()
#define lsb(x) (x & (-x))
#define vi vector<int>
#define YES { cout << "YES" << endl; return; }
#define NO { cout << "NO" << endl; return; }
using ll = long long;
using pii = std::pair<int, int>;
const int NMAX = 1e6;
using namespace std;
char a[NMAX + 5], b[NMAX + 5], ch;
int contrib[NMAX + 5], n, q;
signed main() {
cin.tie(nullptr)->sync_with_stdio(false);
cin >> n >> q;
for (int i = 1; i <= n; ++i)
cin >> a[i];
for (int i = 1; i <= n; ++i)
cin >> b[i];
int S = 0;
for (int i = 1; i <= n; ++i) {
contrib[i] = (b[i] - a[i] + 26) % 26;
S = (S + (i % 2 == 1 ? 1 : -1) * contrib[i] + 26) % 26;
}
cout << (S == 0 ? "da\n" : "ne\n");
for (int i = 0, p; i < q; ++i) {
cin >> p >> ch;
S = (S - (p % 2 == 1 ? 1 : -1) * contrib[p] % 26 + 26) % 26;
a[p] = ch;
contrib[p] = (b[p] - a[p] + 26) % 26;
S = (S + (p % 2 == 1 ? 1 : -1) * contrib[p] % 26 + 26) % 26;
cout << (S == 0 ? "da\n" : "ne\n");
}
return 0;
}
