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#include<bits/stdc++.h>
using namespace std;
inline int read(){
   int s=0,w=1;
   char ch=getchar();
   while(ch<'0'||ch>'9'){if(ch=='-')w=-1;ch=getchar();}
   while(ch>='0'&&ch<='9') s=s*10+ch-'0',ch=getchar();
   return s*w;
}
int a[8003],b[8003],c[8003];
char s[8003];
signed main()
{
	int n=read(),k=read(),t=read(),ans=-1;
	scanf("%s",s+1);
	for(int i=1; i<=n; ++i) a[i]=(a[i-1]+(s[i]=='1'));
	for(int i=1; i<=n; ++i) b[i]=(b[i-1]+(s[i]=='2'));
	for(int i=1; i<=n; ++i) c[i]=(c[i-1]+(s[i]=='3'));
	if(a[n]<=k)
		ans=a[n]+c[n]+min(b[n],k-a[n]);
	for(int i=t; i<=n-t; ++i)
		for(int j=i; j<=n-t; ++j)
		{
			int A=a[i]+a[n]-a[j];
			A+=b[i]-b[i-t]+b[j+t]-b[j];
			int B=b[i-t]+b[n]-b[j+t];
			int C=c[i-t]+c[n]-c[j+t];
			C+=a[i-t]+a[n]-a[j+t];
			if(A<=k) ans=max(ans,min(k-A,B)+C);
		}
	printf("%d\n",ans);
	return 0;
}