def solve(n, k, s):
    # Write your code here
    valid_pairs = 0
    counter = [0]*(n+1)
    
    # at counter[i] there will be count of 1s upto i
    for i, bit in enumerate(s):
        counter[i + 1] = counter[i] + int(bit)
        
    p = 0
    for i, bit in enumerate(s):
        if bit == "1":
            p += counter[min(n, i + k + 1)] - counter[max(0, i - k)]
                     
    total_pairs = n*n           
    gcd_val = math.gcd(p, total_pairs)
    numerator = p//gcd_val
    denominator = total_pairs//gcd_val
    
    return f"{numerator}/{denominator}"