#include<bits/stdc++.h>
using namespace std;
typedef long long LL;
#define FOR(i,a,b) for(int i=(a);i<=(b);++i)
#define FORD(i,a,b) for(int i=(b);i>=(a);--i)
const int MOD=26;
const int N=(int)1e6;
const int INF=(int)1e9+7;
string s1,s2;
int n,q;
int main(){
ios::sync_with_stdio(0);
cin.tie(0); cout.tie(0);
cin>>n>>q;
cin>>s1>>s2;
s1='#'+s1,s2='#'+s2;
int sum=0;
FOR(i,1,n){
sum=(s2[i]-s1[i]+'a'-sum)%MOD;
}
if (sum==0) cout<<"da\n"; else cout<<"ne\n";
while(q--){
int pos; char change;
cin>>pos>>change;
int diff=(change-s1[pos]+'a')%MOD;
s1[pos]=change;
sum=(sum+((n-pos+1)%2==1?-diff:diff)+26)%MOD;
if (sum==0) cout<<"da\n"; else cout<<"ne\n";
}
}
