#include<bits/stdc++.h>
using namespace std;
#define ll long long int
int main(){
char input[8][8];
for(ll i=0;i<8;i++){
for(ll j=0;j<8;j++){
cin>>input[i][j];
}
}
for(ll i=0;i<8;i++){
for(ll j=0;j<7;j++){
if(input[i][j]==input[i][j+1]){
cout<<"NO"; return 0;
}
}
}
cout<<"YES";
}
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