#ifndef _DEBUG
#include <bits/stdc++.h>
#else
#include "bits/stdc++.h"
#endif
using namespace std;
using ll = long long;
using ld = long double;
using VI = vector<int>;
using VL = vector<ll>;
using VS = vector<string>;
template<class T> using PQ = priority_queue<T, vector<T>, greater<T>>;
#define FOR(i,a,n) for(int i=(a);i<(n);++i)
#define eFOR(i,a,n) for(int i=(a);i<=(n);++i)
#define rFOR(i,a,n) for(int i=(n)-1;i>=(a);--i)
#define erFOR(i,a,n) for(int i=(n);i>=(a);--i)
#define SORT(a) sort(a.begin(),a.end())
#define rSORT(a) sort(a.rbegin(),a.rend())
#define fSORT(a,f) sort(a.begin(),a.end(),f)
#define all(a) a.begin(),a.end()
#define out(y,x) ((y)<0||h<=(y)||(x)<0||w<=(x))
#define tp(a,i) get<i>(a)
#ifdef _DEBUG
#define line cout << "-----------------------------\n"
#define stop system("pause")
#endif
constexpr ll INF = 1000000000;
constexpr ll LLINF = 1LL << 60;
constexpr ll mod = 1000000007;
constexpr ll MOD = 998244353;
constexpr ld eps = 1e-10;
constexpr ld pi = 3.1415926535897932;
template<class T>inline bool chmax(T& a, const T& b) { if (a < b) { a = b; return true; }return false; }
template<class T>inline bool chmin(T& a, const T& b) { if (a > b) { a = b; return true; }return false; }
inline void init() { cin.tie(nullptr); cout.tie(nullptr); ios::sync_with_stdio(false); cout << fixed << setprecision(15); }
template<class T>inline istream& operator>>(istream& is, vector<T>& v) { for (auto& a : v)is >> a; return is; }
template<class T, class U>inline istream& operator>>(istream& is, pair<T, U>& p) { is >> p.first >> p.second; return is; }
template<class T>inline vector<T> vec(size_t a) { return vector<T>(a); }
template<class T>inline vector<T> defvec(T def, size_t a) { return vector<T>(a, def); }
template<class T, class... Ts>inline auto vec(size_t a, Ts... ts) { return vector<decltype(vec<T>(ts...))>(a, vec<T>(ts...)); }
template<class T, class... Ts>inline auto defvec(T def, size_t a, Ts... ts) { return vector<decltype(defvec<T>(def, ts...))>(a, defvec<T>(def, ts...)); }
template<class T>inline void print(const T& a) { cout << a << "\n"; }
template<class T, class... Ts>inline void print(const T& a, const Ts&... ts) { cout << a << " "; print(ts...); }
template<class T>inline void print(const vector<T>& v) { for (int i = 0; i < v.size(); ++i)cout << v[i] << (i == v.size() - 1 ? "\n" : " "); }
template<class T>inline void print(const vector<vector<T>>& v) { for (auto& a : v)print(a); }
inline string reversed(const string& s) { string t = s; reverse(all(t)); return t; }
template<class T>inline T sum(const vector<T>& a, int l, int r) { return a[r] - (l == 0 ? 0 : a[l - 1]); }
template<class T>inline void END(T s) { print(s); exit(0); }
void END() { exit(0); }

template<class Op> class SegmentTree {
	using T = typename Op::T;
	int len, n;
	vector<T> dat;
public:
	SegmentTree(const int _n) : n(_n) {
		for (len = 1; len < n; len <<= 1);
		dat.resize(len << 1, Op::unit);
	}
	SegmentTree(const vector<T>& v) : n(v.size()) {
		for (len = 1; len < n; len <<= 1);
		dat.resize(len << 1, Op::unit);
		for (int i = 0; i < n; ++i)dat[i + len] = v[i];
		for (int i = len - 1; 0 < i; --i)
			dat[i] = Op::merge(dat[i << 1], dat[i << 1 | 1]);
	}
	inline void update(int idx, const T a) {
		idx += len;
		dat[idx] = Op::update(dat[idx], a);
		for (idx >>= 1; 0 < idx; idx >>= 1)
			dat[idx] = Op::merge(dat[idx << 1], dat[idx << 1 | 1]);
	}
	inline T value(int l, int r) {
		T vl = Op::unit, vr = Op::unit;
		for (l += len, r += len; l < r; l >>= 1, r >>= 1) {
			if (l & 1)vl = Op::merge(vl, dat[l++]);
			if (r & 1)vr = Op::merge(dat[--r], vr);
		}
		return Op::merge(vl, vr);
	}
	inline T operator[](int idx) { return dat[idx + len]; }
};
template<class Type> struct node {
	using T = Type;
	inline static T unit = 0;
	inline static T merge(T vl, T vr) { return vl + vr; }
	inline static T update(T vl, T vr) { return vl + vr; }
};

int main() {
	init();

	int n, k; cin >> n >> k;
	string s; cin >> s;
	s = "o" + s;
	SegmentTree<node<int>> dp(n + 1);
	rFOR(i, 0, n) {
		if (s[i] == 'o' && dp.value(i + 1, min(n + 1, i + k + 1)) == 0)dp.update(i, 1);
	}
	eFOR(i, 1, k)if (dp[i])END(i);
	END(0);

	return 0;
}