long gcd(long a, long b)
{
  if (b == 0) return a;
  return gcd(b, a % b);
}

string solve(long n, int k, string s)
{
  int a=0,b;
  long cnt=0,sum=0;
  for (b = 0; b <= k; b++) 
    if (s[b]=='1') sum++;
  for(a=0,b=k+1;a<n;a++,b++) {
    if (s[a]=='1') cnt+=sum;
    if (a>=k) sum-=s[a-k]=='1';
    if (b<n) sum+=s[b]=='1';
  }
  long nxn = n * n, div = gcd(cnt, nxn);
  cnt /= div, nxn /= div;
  return to_string(cnt) + "/" + to_string(nxn);
}

def solve(N, K, S):   
    S = [int(b) for b in S]
    rolling_sum = sum(S[0:K])
    numerator = 0
    for i in range(N):
        if i > K:
            rolling_sum = rolling_sum - S[i-K-1]
        if i < N - K:
            rolling_sum = rolling_sum + S[i+K]
        if S[i]:
            numerator = numerator + rolling_sum
            
    denominator = N**2
    d = math.gcd(numerator, denominator)    
    return f'{numerator//d}/{denominator//d}'

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}"

def solve(n, k, s):

    s= [int(x) for x in s]
    rolling_sum=sum(s[:k+1])
 
    num_pairs=0
    for i in range(k,n+k):
        if s[i-k]:
            num_pairs+=2*rolling_sum-1
            rolling_sum-=1
        if i+1<n:
            rolling_sum+=s[i+1]
    
    d=math.gcd(num_pairs, n**2)
    
    return f'{int(num_pairs/d)}/{int(n**2/d)}'