In this question, there are only $$$2$$$ types of chess boards possible, starting with white and starting with black. So we can check this $$$2$$$ cases manually. Another approach is to check that now to adjacent cells have same color.

#include <bits/stdc++.h>
using namespace std;
 
int main(){
    string str[8];
    for(int i=0;i<8;i++){
        cin>>str[i];
    }
    int check1=1,check2=1;
    for(int i=0;i<8;i++){
        for(int j=0;j<8;j++){
            if(((str[i][j]-'0'))!=((i%2)^(j%2))){
                check1=0;
            }
        }
    }
    for(int i=0;i<8;i++){
        for(int j=0;j<8;j++){
            if((str[i][j]-'0')!=((i%2)^(j%2)^1)){
                check2=0;
            }
        }
    }
    if(check1 || check2){
        cout<<"YES"<<endl;
    }
    else{
        cout<<"NO"<<endl;
    }
}