function getValue(a,xor) {
    if(xor === 0) {
        if(a === 0) return 0;
        if(a === 1) return 1;
    }
    if(xor == 1) {
        if(a === 0) return 1;
        if(a === 1) return 0;        
    }
}
function cipher(k, s) {
    // Write your code here
    let n = s.length - k + 1;
    let arr = Array(n).fill(-1);
    arr[0] = parseInt(s[0]);
    let i=1;
    let currentXor = 0;
    while(i<n) {
        let left = i - k + 1 >= 0 ? i - k + 1 : 0;
        if(left > 0) {
            currentXor ^= arr[left-1]; 
        }
        currentXor ^= arr[i-1];
        arr[i] = getValue(currentXor, parseInt(s[i]));
        i++;
    }
    return arr.join('');
}