This submission is migrated from previous version of oj.uz, which used different machine for grading. This submission may have different result if resubmitted.
//#pragma GCC target("sse,sse2,sse3,ssse3,sse4,popcnt,abm,mmx,avx,tune=native")
//#pragma GCC optimize("Ofast,unroll-loops,fast-math,O3")
 
#include<bits/stdc++.h>	
 
using namespace std;
 
#define all(a) a.begin(), a.end()                                                   
#define rall(a) a.rbegin(), a.rend()                 
#define sz(a) (int)a.size()
#define s second
#define f first
 
using ll = long long;
using pii = pair<int, int>;
using pll = pair<ll, ll>;
 
mt19937_64 rng(chrono::steady_clock::now().time_since_epoch().count());
     
vector<pii> rid = {{0, 1}, {0, -1}, {1, 0}, {-1, 0}};
vector<pii> dir = {{-1, -1}, {-1, 1}, {1, -1}, {1, 1}};
 
const int N = 5e5 + 1, mod = 998244353;
 
const ll inf = 1e9;
 
double eps = 1e-15;
                                                
bool flg = 0;
void slv() {
	int n, q;
	cin >> n >> q;
	string a, b;
	cin >> a >> b;
	int v[n + 1], sum[2];
	sum[0] = sum[1] = 0;
	for (int i = 1; i <= n; i++) {
		v[i] = a[i - 1] - b[i - 1];
		sum[i & 1] += v[i];
 	}
 	if ((sum[0] % 26 + 26) % 26 == (sum[1] % 26 + 26) % 26) cout << "da\n";
 	else cout << "ne\n";
 	while (q--) {
 		int p;
 		char c;
 		cin >> p >> c;
 		sum[p & 1] -= v[p];
 		a[p - 1] = c;
 		v[p] = a[p - 1] - b[p - 1];
 		sum[p & 1] += v[p];
	 	if ((sum[0] % 26 + 26) % 26 == (sum[1] % 26 + 26) % 26) cout << "da\n";
 		else cout << "ne\n";
 	}
}                                                                    
 
main() {
	//freopen("input.txt", "r", stdin);                                                                                     
	//freopen("output.txt", "w", stdout);                                                                                     
	ios_base::sync_with_stdio(0);	                                                                                       
	cin.tie(0);
	int tp = 1;
	if (flg) cin >> tp;
	while (tp--) {  	
		slv();
	}
}
//wenomechainsama      
Compilation message (stderr)
Main.cpp:57:1: warning: ISO C++ forbids declaration of 'main' with no type [-Wreturn-type]
   57 | main() {
      | ^~~~| # | Verdict | Execution time | Memory | Grader output | 
|---|
| Fetching results... | 
| # | Verdict | Execution time | Memory | Grader output | 
|---|
| Fetching results... | 
| # | Verdict | Execution time | Memory | Grader output | 
|---|
| Fetching results... | 
| # | Verdict | Execution time | Memory | Grader output | 
|---|
| Fetching results... | 
| # | Verdict | Execution time | Memory | Grader output | 
|---|
| Fetching results... | 
| # | Verdict | Execution time | Memory | Grader output | 
|---|
| Fetching results... |