#include<iostream>

using namespace std;

long long mod = 1e9+7;
long long fact[1234];

long long inv(long long x)
{
  long long ex = mod-2;
  long long pw = x;
  long long ans = 1;
  while(ex)
  {
    if(ex%2)
      ans = (ans*pw)%mod;
    pw = (pw*pw)%mod;
    ex /= 2;
  }
  return ans;
}

long long komb(long long a, long long b)
{
  if(a < b || a < 0 || b < 0)
    return 0;
  return (fact[a]*(inv((fact[b]*fact[a-b])%mod)%mod))%mod;
}

long long n, k;
int bits[1234], mabits[1234];
long long maxans = 0, minans = 0;

long long solve(long long n2, long long k2)
{
  if(n2 == 0)
    return k2 == 0;
  if(k2 == 0)
    return 1;
  if(mabits[n2-1])
    return (komb(n2-1, k2)+solve(n2-1, k2-1))%mod;
  return solve(n2-1, k2);
}

long long solve2(long long n2, long long k2)
{
  if(n2 == 0)
    return k2 == 0;
  if(k2 == 0)
    return 1;
  if(bits[n2-1])
    return (komb(n2-1, k2)+solve2(n2-1, k2-1))%mod;
  return solve2(n2-1, k2);
}

int main(int argc, char const *argv[]) {
  // for (int i = 0; i < 1234; ++i) {
  //   fact[i] = 0;
  //   bits[i] = 0;
  //   mabits[i] = 0;
  // }


  cin>>n>>k;
  fact[0] = 1;
  for(int i = 1; i <= n; i++)
    fact[i] = (fact[i-1]*i)%mod;
  // cout<<komb(n, k)<<endl;
  char c;
  for(int i = n-1; i >= 0; i--)
  {
    cin>>c;
    bits[i] = 0;
    if(c == '1')
      bits[i] = 1;
  }
  int carry = 0;
  for(int i = 0; i < n; i++)
  {
    mabits[i] = (bits[i]+carry+1)%2;
    carry = (bits[i]+carry+1)/2;
  }
  mabits[n] = carry;
  int k2 = k;
  // for(int i = n; i >= 0; i--) {
  //   cout<<mabits[i];
  // }
  // cout<<endl << endl;
  // for(int i = n; i >= 0; i--)
  // {
  //   if(mabits[i])
  //   {
  //     maxans = (maxans+komb(i, k2))%mod;
  //     k2--;
  //   }
  // }
  // k2 = k;
  // for(int i = n; i >= 0; i--)
  // {
  //   if(bits[i])
  //   {
  //     minans = (minans+komb(i, k2))%mod;
  //     k2--;
  //   }
  // }
  maxans = solve(n+1, k);
  minans = solve2(n, k);
  int popc = 0;
  for(int i = 0; i < n; i++)
    popc += bits[i];
  if(popc == k)
    minans--;
  // cout<<maxans<<" "<<minans<<endl;
  cout<<(maxans+mod-minans)%mod<<endl;
  return 0;
}