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#include <bits/stdc++.h>
using namespace std;
#define rep(i,a,n) for (int i=(a);i<(n);i++)
#define per(i,a,n) for (int i=(n)-1;i>=(a);i--)
#define pb push_back
#define eb emplace_back
#define mp make_pair
#define all(x) (x).begin(),(x).end()
#define fi first
#define se second
#define SZ(x) ((int)(x).size())
typedef vector<int> VI;
typedef basic_string<int> BI;
typedef long long ll;
typedef pair<int,int> PII;
typedef double db;
mt19937 mrand(1111); 
const ll mod=1000000007;
int rnd(int x) { return mrand() % x;}
ll powmod(ll a,ll b) {ll res=1;a%=mod; assert(b>=0); for(;b;b>>=1){if(b&1)res=res*a%mod;a=a*a%mod;}return res;}
ll gcd(ll a,ll b) { return b?gcd(b,a%b):a;}
// head

const int N=8100;
int n,k,t,p[N][3];
char s[N];

int main() {
	scanf("%d%d%d",&n,&k,&t);
	scanf("%s",s+1);
	rep(i,1,n+1) {
		rep(j,0,3) p[i][j]=p[i-1][j];
		p[i][s[i]-'1']++;
	}
	int ans=-1;
	if (p[n][0]<=k) {
		ans=p[n][0]+min(k-p[n][0],p[n][1])+p[n][2];
	}
	for (int i=1;i+2*t-1<=n;i++) for (int j=i+t;j+t-1<=n;j++) {
		int c=p[i+t-1][1]-p[i-1][1]+p[i+t-1][0]-p[i-1][0]+
		p[j+t-1][1]-p[j-1][1]+p[j+t-1][0]-p[j-1][0];
		int r0=p[i-1][0]+p[n][0]-p[j+t-1][0];
		int r1=p[i-1][1]+p[n][1]-p[j+t-1][1];
		int r2=p[i-1][2]+p[n][2]-p[j+t-1][2];
		/*if (i==4&&j==7) {
			printf("%d %d %d %d\n",c,r0,r1,r2);
			printf("-- %d %d %d\n",p[i-1][0],p[j-1][0]-p[i+t-1][0],p[n][0]-p[j+t-1][0]);
		}*/
		c+=r0;
		if (c>k) continue;
		ans=max(ans,r0+min(k-c,r1)+r2);
		// i ... i + t - 1 上班
		// i 
	}
	printf("%d\n",ans);
}