#include <bits/stdc++.h>
using namespace std;
using ll = long long;
void yesno(int x) { cout << (x ? "da\n" : "ne\n"); }
int main() {
ios::sync_with_stdio(false);
cin.tie(nullptr);
int n, k;
string s, t;
cin >> n >> k >> s >> t;
ll f = 0, f1 = 0;
auto norm = [&](ll &x) {
x %= 26;
if (x < 0)
x += 26;
};
auto val = [&](char c) -> int { return c - 'a'; };
for (int i = 0; i < n; ++i) {
if (i & 1) {
f -= val(s[i]);
f1 -= val(t[i]);
} else {
f += val(s[i]);
f1 += val(t[i]);
}
}
norm(f);
norm(f1);
yesno(f1 == f);
while (k--) {
int x;
char a;
cin >> x >> a, --x;
int old = val(s[x]);
int neww = val(a);
if (x & 1 ^ 1) {
f += neww - old;
} else {
f += old - neww;
}
norm(f);
yesno(f == f1);
s[x] = a;
}
return 0;
}
