#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
typedef long double ld;
typedef pair<ll,ll> pl;
typedef pair<int,int> pii;
typedef tuple<int,int,int> tt;
#define all(a) a.begin(), a.end()
#define filter(a) a.erase(unique(all(a)), a.end())
int add (int a, int b) {
assert(0 <= a && a < 26 && 0 <= b && b < 26);
return a + b - (a + b < 26 ? 0 : 26);
}
int sub (int a, int b) {
assert(0 <= a && a < 26 && 0 <= b && b < 26);
return a - b + (a - b >= 0 ? 0 : 26);
}
int mul (int a, int b) {
assert(0 <= a && a < 26 && 0 <= b && b < 26);
return 1LL * a * b % 26;
}
struct IT {
vector<pii> tr;
IT (int sz) : tr(4 * sz) {}
pii opr (pii a, pii b) {
return {mul(a.first, b.first), add(mul(a.first, b.second), a.second)};
}
void update (int pos, pii val, int k, int l, int r) {
if (pos < l || r < pos) return;
if (l == r) return tr[k] = val, void();
int mid = (l + r) >> 1;
update(pos, val, 2 * k, l, mid);
update(pos, val, 2 * k + 1, mid + 1, r);
tr[k] = opr(tr[2 * k], tr[2 * k + 1]);
}
bool valid() { return tr[1].second == 0; }
};
int main()
{
ios::sync_with_stdio(0);
cin.tie(0);
int n, q; cin >> n >> q;
string s, t; cin >> s >> t;
s = " " + s, t = " " + t;
IT tree(n);
for (int i = 1; i <= n; i++) {
int val = sub(t[i] - 'a', s[i] - 'a');
tree.update(i, make_pair(sub(0, 1), val), 1, 1, n);
}
cout << (tree.valid() ? "da" : "ne") << "\n";
while (q--) {
int p; char c; cin >> p >> c;
int val = sub(t[p] - 'a', c - 'a');
s[p] = c;
tree.update(p, make_pair(sub(0, 1), val), 1, 1, n);
cout << (tree.valid() ? "da" : "ne") << "\n";
}
return 0;
}
