#include <bits/stdc++.h>
#include<ext/pb_ds/assoc_container.hpp>
using namespace std;
//typedef tree<int, null_type, less<int>, rb_tree_tag, tree_order_statistics_node_update > ordered_set ;
#define int long long
#define F first
#define S second
#define rep(i , j , n ) for(int i = j ;i < n; i++ )
#define FOR(i , n ) rep(i ,0 , n )
#define sz size()
#define pb push_back
#define all(x) x.begin() , x.end()
#define vi vector<int>
#define yes cout<<"YES\n";
#define no cout<<"NO\n";
#define cans cout<<ans<<endl;
#define forx(i, x) for(auto i : x)
#define fast
#define pii pair<int ,int >
#define endl "\n"
#define sp ' '
const int N = 300 ;
const int inf = 1e15 ;
//int rec(int a , int b , int c, int d ){
//if(a+b+c+d == 0 )
//return 1 ;
//int ans = 0 ;
//if( ((a%2)^(2 * ( b%2 ) ) ^( 3 * (c%2 ) ) ^(4 * ( d%2 ) )) == 0 ) {
//ans = 1 ;
//}
// if(a)ans += rec(0 , b , c , d ) ;
// if(b)ans += rec(a , 0 , c , d ) ;
// if(c)ans += rec(a , b , 0 , d ) ;
// if(d)ans += rec(a , b , c , 0 ) ;
// return ans ;
//
//}
main()
{
int n, q ;
cin>> n >> q ;
string s, s1 ;
cin>> s >> s1 ;
int a[n] ;
int a1[n] ;
FOR(i, n )a[i] = s[i] - 'a' ;
FOR(i, n )a1[i] = s1[i] - 'a' ;
FOR(i, n-1 )
{
if(a[i] != a1[i] )
{
int temp = (a1[i] + 26 ) - a[i] ;
a[i] += temp ;
a[i+1]+=temp ;
a[i]%=26 ;
a[i+1]%=26 ;
}
}
bool ok= 1;
FOR(i, n )
{
if(a[i]!=a1[i])ok = 0 ;
}
if(ok)cout<<"da\n";
else cout<<"ne\n" ;
while(q--)
{
int idx; char v ;
cin >> idx >> v ;
idx--;
s[idx] = v ;
// cout<<s<<endl<<s1;
FOR(i, n )a[i] = s[i] - 'a' ;
FOR(i, n )a1[i] = s1[i] - 'a' ;
FOR(i, n-1 )
{
if(a[i] != a1[i] )
{
int temp = (a1[i] + 26 ) - a[i] ;
a[i] += temp ;
a[i+1]+=temp ;
a[i]%=26 ;
a[i+1]%=26 ;
}
}
ok= 1;
FOR(i, n )
{
if(a[i]!=a1[i])ok = 0 ;
}
if(ok)cout<<"da\n";
else cout<<"ne\n" ;
}
return 0 ;
}
