string fairRations(vector B) {

 int res = 0;
 // size1 = sizeof(B)/sizeof(B[0]);
for(int i = 0; i < B.size()- 1; i++){
    if(B[i] % 2 == 1){
        B[i+1]++;
        res+=2;
    }
}
return B[B.size() - 1] % 2 == 0 ? to_string(res) : "NO";

}