#include <bits/stdc++.h>

using namespace std;

#define fore(i, a, b) for(int i = a, bella = b; i < bella; i++)
#define mset(a, b) memset(a, b, sizeof(a))
#define ALL(a) a.begin(), a.end()
#define SZ(a) int(a.size())
#define fst first
#define snd second
#define pb push_back
#define FIO ios::sync_with_stdio(0); cin.tie(0)

typedef long double ld;
typedef long long ll;
typedef pair<int, int> ii;
typedef vector<int> vi;

const int MAXN = 2e5 + 7;
const int MAXK = 5;
const int INF = 1e6;

// Input global values
string s;
int n, m, k;
bool dbg = false;

// DP Aux functions
int izq[MAXN];
void izq_init() {
    int pos = 0;
    fore(i, 0, n) {
        izq[i] = pos;
        if(i+1 != n && (s[i] == '0' || s[i+1] == '0'))
            pos = i+1;
    }
    
    fore(i, 0, n)
        assert(s[izq[i]] == s[i] && (izq[i] == 0 || s[i] == '0' || s[izq[i] - 1] == '0'));
}

int cnt_arr[MAXN];
void cnt_init() {
    fore(i, 0, n) {
        cnt_arr[i] = (i ? cnt_arr[i-1] : 0) + (s[i] == '1');
    }
}
int cnt(int i, int j) {
    assert(i <= j);
    return cnt_arr[j] - (i ? cnt_arr[i-1] : 0);
}

// DP
int dp[MAXN][MAXK];
void dp_init() {
    mset(dp, -1);
}
int dp_do(int pos, int act_k, const int &act_val) {
    if(act_k == 0)
        return 0;

    if(pos < 0)
        return INF;

    int &res = dp[pos][act_k];
    if(res != -1)
        return res;

    res = dp_do((s[pos] == '1' ? izq[pos] - 2 : pos - 1), act_k, act_val);
    if(pos - act_val + 1 >= 0) {
        assert(act_val >= cnt(pos - act_val + 1, pos));

        res = min(
            res,
            act_val - cnt(pos - act_val + 1, pos) +
                dp_do(izq[pos - act_val + 1] - 2, act_k - 1, act_val)
        );
    }

    assert(res >= 0);

    return res;
}

bool check(int bm) {
    dp_init();

    int dp_val = dp_do(n-1, k, bm);

    return dp_val <= m;
}

int main() {
    FIO;

    cin >> n >> m >> k;
    cin >> s;

    izq_init();
    cnt_init();

    int bs = 1, be = n + 1;
    while(bs + 1 < be) {
        int bm = (bs + be)/2;
        
        if(check(bm))
            bs = bm;
        else be = bm;
    }
    if(check(be))
        bs = be;

    cout << (check(bs) ? bs : -1) << '\n';

    return 0;
}