#include <iostream>
#include <vector>
#include <string>
#include <algorithm>
using namespace std;

typedef long long ll;

int main()
{
	ll N, K; string S;
	cin >> N >> K >> S;
	if (K < S.size())
		S.resize(K);
	else
	{
		string s = S;
		while (S.size() < K)
			S += s;
		S.resize(K);
	}
	reverse(S.begin(), S.end());	//ひっくり返した方が楽

	int ans = 0;
	int left = 0;
	while (!S.empty())
	{
		if (left == 0)
		{
			++ans;
			if (S.back() == '1')
				++left;
			else if (S.back() == '2')
				left = left + 2;
			S.pop_back();
		}
		else
		{
			while (!S.empty() && left != 0)
			{
				if (S.back() == '1')
					++left;
				else if (S.back() == '2')
					left = left + 2;
				S.pop_back();
				--left;
			}
		}
	}

	cout << ans << endl;

	return 0;
}