#include <bits/stdc++.h>

#define int int64_t

using namespace std;

int mod = 1e9 + 7;

int32_t main() {
    ios_base::sync_with_stdio(false);
    int n, k;
    cin >> n >> k;
    string s;
    cin >> s;
    vector<int> dp(n);
    dp[0] = 1;
    for (int i = 1; i < n; i++) {
        if (s[i - 1] == 'X') {
            continue;
        }
        for (int j = 1; j <= k && j <= i; j++) {
            (dp[i] += dp[i - j]) %= mod;
        }
    }
    cout << dp[n - 1] << '\n';
}