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#include <bits/stdc++.h>
using namespace std;

#define REP(i, n) for (int i = 0; i < (n); ++i)
#define EACH(it, cont) for (auto &it : cont)
#define FOR(i, b, e)  for (int i = (b); i <= (e); ++i)
#define FORD(i, b, e) for (int i = (b); i >= (e); --i)
#define ALL(c)   begin(c), end(c)

#define dump     fancy_dumper::DumpFirst<&std::cerr>(),
#define say      fancy_dumper::DumpFirst<&std::cout>(),
#define $dump    fancy_dumper::Dumper<&std::cerr>
#define $say     fancy_dumper::Dumper<&std::cout>
#define $(x) #x, fancy_dumper::ToggleSeparator(), (x),\
				 fancy_dumper::ToggleSeparator()

namespace fancy_dumper {

struct ToggleSeparator { };

template<std::ostream *Out>
struct DumpFirst { };

template<std::ostream *Out>
struct Dumper {
	static void *&last() {
		static void *p;
		return p;
	}
	static const char *&separator() {
		static const char *s = " ";
		return s;
	}
	static const char *&separatorNewLine() {
		static const char *s = "\n";
		return s;
	}
	static const char *&unseparator() {
		static const char *s = "=";
		return s;
	}
	Dumper() {
		last() = this;
	}
	~Dumper() {
		if (this == last()) {
			*Out << separatorNewLine();
			last() = 0;
		}
	}
	Dumper operator, (ToggleSeparator) {
		std::swap(separator(), unseparator());
		return Dumper();
	}
};

template<std::ostream *Out, class T>
Dumper<Out> operator,(Dumper<Out>, const T &e) {
	*Out << Dumper<Out>::separator() << e;
	return Dumper<Out>();
}

template<std::ostream *Out, class T>
Dumper<Out> operator, (DumpFirst<Out>, const T &e) {
	*Out << e;
	return Dumper<Out>();
}

}

namespace std {

template<class T, class Y>
std::ostream &operator<< (std::ostream &o, const std::pair<T, Y> &p) {
	return o << p.first << ' ' << p.second;
}

template<class T>
std::ostream &operator<< (std::ostream &o, const std::vector<T> &v) {
	bool isBegin = true;
	EACH (e, v) {
		if (!isBegin) { o << ' '; }
		isBegin = false;
		o << e;
	}
	return o;
}

template<class T>
std::ostream &operator<< (std::ostream &o, const std::set<T> &v) {
	bool isBegin = true;
	EACH (e, v) {
		if (!isBegin) { o << ' '; }
		isBegin = false;
		o << e;
	}
	return o;
}

} // ns std

template<class T>
std::ostream &operator,(std::ostream &o, const T &t) {
	return o << t;
}

struct StdinReader {
	StdinReader() { std::ios::sync_with_stdio(0); }
} stdinReader;
#define get stdinReader,

template<class T> StdinReader &operator, (StdinReader &sr, T &t) { std::cin >> t; return sr; }
template<class T> StdinReader &operator, (StdinReader &sr, std::vector<T> &v) { EACH (x, v) sr, x; return sr; }
template<class T, class U> StdinReader &operator, (StdinReader &sr, std::pair<T, U> &p) { return sr, p.first, p.second; }

struct GetSizeHelper {
	int s;
	operator int  () const { return s; }
	operator bool () const { return s; }
	template<class T> GetSizeHelper(const T &t) : s((int) size(t)) {}
};
#define isize (GetSizeHelper)
template <class T, class U> bool remin(T &a, const U &b) { return b < a ? a = b, true : false; }
template <class T, class U> bool remax(T &a, const U &b) { return b > a ? a = b, true : false; }

const int inf = 1000000001;
using ll = long long;

// code starts here

struct Pra {
	int n, k, t;

	struct Cnt {
		int c1, c2;
	};
	vector<Cnt> C;

	Pra() {
		get n, k, t;
		string s;
		s.reserve(n+1);
		C.resize(n+1);
		get s;
		init(s);
	}

	void init(const string &s) {
		FORD (i, n-1, 0) {
			C[i].c1 = C[i+1].c1 + (s[i] == '1');
			C[i].c2 = C[i+1].c2 + (s[i] == '2');
		}
	}

	int R2(int b, int e) const {
		return C[b].c2 - C[e].c2;
	}

	int R12(int b, int e) const {
		return C[b].c1 - C[e].c1 + R2(b, e);
	}

	int solve() {
		int M = R12(0, n); // all meetings
		int reqm = max(0, M - k);
		int remotem = R2(0, n);

		// stay home whole day
		if (remotem >= reqm) {
			dump "shwd", $(M), $(reqm), $(remotem);
			return n - reqm;
		}

		// get to work
		int ans = -1;
		FOR (t0, 0, n - 2*t - 1) {
			const int bm = R2(0, t0); // remote m. prior to h → w travel
			FOR (t1, t0 + 2*t + 1, n) {
				dump $(t0), $(t1);
				int am = R2(t1, n); // remote m. after to w → h travel
				int wm = R12(t0+t, t1-t); // all m. during w

				if (bm + am + wm < reqm)
					continue;

				if (remax(ans, n - (t1-t0) - max(0, reqm - wm))) {
					static int dbg;
					if (dbg++ < 100)
						dump $(t0), $(t1), $(bm), $(am), $(wm), $(M), $(reqm), $(ans);
				}
			}
		}
		return ans;
	}
};

//~ pkitszel-desk pra $ ./pra <2.in
//~ t0=0 t1=5
//~ t0=0 t1=6
//~ t0=0 t1=7
//~ t0=0 t1=7 bm=0 am=0 wm=2 M=2
//~ t0=1 t1=6
//~ t0=1 t1=7
//~ t0=2 t1=7
//~ 1

//~ 01234567
//~ 3313233
//~ tt...tt

int main() {
	Pra p;
	say p.solve();
}