#include<bits/stdc++.h>
#define LL long long
#define LD long double
#define fr(x) freopen(#x".in","r",stdin);freopen(#x".out","w",stdout);
using namespace std;
const int N=2e6+5;const LD eps=1e-12;
int T,n,m,p[N];LD k,a[N];char C[N];
int main()
{
	scanf("%d",&T);
	for(int tt=1;tt<=T;tt++)
	{
		scanf("%d%Lf%s",&n,&k,C);int w=1e9;p[0]=0;
		for(int i=1;i<=n;i++) a[i]=a[i-1]+C[i-1]-'0'-k,p[i]=i;
		sort(p,p+1+n,[](int x,int y){return a[x]<a[y];});LD ans=1e9;
		for(int i=1;i<=n;i++) ans=min(ans,fabsl((LD)(a[p[i]]-a[p[i-1]])/(p[i]-p[i-1])));
		for(int i=1;i<=n;i++) if(fabsl(fabsl((LD)(a[p[i]]-a[p[i-1]])/(p[i]-p[i-1]))-ans)<eps)
			w=min(w,min(p[i],p[i-1])+1);
		printf("Case #%d: %d\n",tt,w-1);
	}
	return 0;
}