def fairRations(B):
    count=0
    # Write your code here
    def isEvens(arr):
        for i in arr:
            if i%2 != 0:
                return False
        return True
    for j in range(len(B)):
        if B[j] % 2 != 0:
            if j == len(B)-1:
                return 'NO'
            B[j]+=1
            B[j+1]+=1
            count+=2
            if isEvens(B):
                return str(count)
    return '0'
            

string fairRations(vector<int> B) {
    int res = 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";
}

string fairRations(vector<int> B) {
    int res = 0;
    for(int i = 0; i < B.size() - 1; i++){
        B[i+1] += B[i] % 2;
        res += B[i] % 2;
    }
    return B[B.size() - 1] % 2 == 0 ? to_string(res*2) : "NO";
}

string fairRations(vector<int> B) {
    int cost = 0;
    int oddIndex = -1;
    
    for (size_t i = 0; i < B.size(); i++) {
        if (B[i] % 2 == 0) {
            continue;
        }
        // Everything from here is ODD...
        if (oddIndex == -1) {
            oddIndex = i;
            continue;
        }
        // Odd Index is never -1 after this...
        cost = cost + i - oddIndex;
        oddIndex = -1;
    }
    
    if (oddIndex != -1) {
        return "NO";
    }
    
    return to_string(cost * 2);
}

public static String fairRations(List<Integer> B) {
        int[] arr = B.stream().mapToInt(Integer::intValue).toArray();
        int count = 0;
        for(int i = 0; arr.length>1 && i< arr.length; i++){
            if(arr[i]%2 != 0 && i + 1 < arr.length) {
                arr[i]++;
                arr[i + 1]++;
                count += 2;
            }
        }
        return arr[arr.length-1]%2 == 0 ? String.valueOf(count) : "NO";
    }