#include <iostream>
#include <vector>
#include <algorithm>

#define LL long long

using namespace std;

vector<LL> as;
LL P = 1000000000 + 7;
LL N, K;
vector<LL> fermat(1005);

LL mocni(LL a, LL b) {
    LL moc = a;
    LL vys = 1;
    while (b > 0) {
        if (b % 2 == 1) {
            vys *= moc;
            vys %= P;
        }
        moc *= moc;
        moc %= P;
        b /= 2;
    }
    return vys;
}

LL spoc() {
    LL total = 0;

    for(LL i = 0; i < as.size(); ++i) {
        LL a = as[i];
        LL k = K - i;
        if (k < 0)
            break;
        //cout << "n nad k" << a << " " << k;
        
        LL nFac = 1;
        if (a != 0 || k != 0) {    
            for (LL nas = a - k + 1; nas <= a; ++nas) {
                nFac *= nas;
                nFac %= P;
            }
        }
        //cout << " = " << (nFac * fermat[k]) % P << endl;
        total += (nFac * fermat[k]) % P;
    }
    
    //cout << total << endl;
    if (as.size() == K) {
        //total -= 1;
        if (total < 0) {
            total += P;
        }
    }
    return total;
}

int main() {
    cin >> N >> K;
    for (LL i = 0; i < N; ++i) {
        char c;
        cin >> c;
        if (c == '1') {
            as.push_back(N - i - 1);
        }
    }
   
    //for (auto&&k : as) {
    //    cout << k << " ";
    //}
    //cout << endl;
    // (K!)^(P - 2)
    fermat[0] = 1;
    LL fac = 1;
    for (LL i = 1;  i <= K; ++i) {
        fac *= i;
        fac %= P;
        fermat[i] = mocni(fac, P - 2);
    }
    
    LL fX = spoc();
    as.insert(as.begin(),N);
    LL fXN = spoc();
    LL total = fXN - fX;
    if (total < 0) {
        total += P;
    }
    cout << total << endl;
    return 0;
}