/*
 * @Author: Linmobi & TLE_Automaton & ChinoKafuu
 * @Date: 2024-11-16 09:46:24
 * @LastEditors: Linmobi
 * @LastEditTime: 2024-11-16 10:18:27
 * @FilePath: /A.cpp
 * @Description: Right Output ! & Accepted !
 */
#include<bits/stdc++.h>
// #define int long long

typedef long long ll;
typedef unsigned long long ull;
typedef std::pair<int, int> pii;

#define rep(i, a, b) for(int i = (a);i <= (b);i++)
#define per(i, a, b) for(int i = (a);i >= (b);i--)
#define rp(i, a) for(int i = 1; i <= (a); i++)
#define pr(i, a) for(int i = (a); i >= 1; i--)
#define go(i, x) for(auto i : x)
#define lowbit(x) (x & (-x))

#define mp make_pair
#define pb push_back
#define gc getchar
#define fir first
#define sec second

using namespace std;

const int P = 1e9 + 7, L = 1e6 + 5, inf = 2e9 + 5;

inline ll qpow(ll a, ll b) { ll ans = 1, q = a; while(b) { if(b & 1) { ans *= q; ans %= P; } q *= q; q %= P; b >>= 1; } return ans; }
inline ll gcd(ll x, ll y) { return y ? gcd(y, x % y) : x; }
inline ll lcm(ll x, ll y) { return x / gcd(x, y) * y; }

namespace fast_IO {
    template<typename T> inline void rd(T &x) {
        x = 0; bool f = 0; char ch = getchar();
        while (! isdigit(ch)) f |= (ch == '-'), ch = getchar();
        while (isdigit(ch)) x = (x << 3) + (x << 1) + ch - '0', ch = getchar();
        x = (f ? - x : x);
    }
    
    template<typename T, typename... Args> inline void rd(T &first, Args& ... args) {
        rd(first);
        rd(args...);
    }
 
    template<typename T> inline void write(T x, bool f) {
        if (x < 0) x = -x, putchar('-'); static short Stack[50], top(0);
        do Stack[++ top] = x % 10, x /= 10; while (x);
        while (top) putchar(Stack[top --] | 48);
        (f ? putchar('\n') : putchar(' '));
    }
} using namespace fast_IO;

namespace fenwick { 
    int t[L];
    void add(int w, int num) {
        while(w < L) t[w] += num, w += lowbit(w);
    }
    int query(int w) {
        int sum = 0;
        while(w) sum += t[w], w -= lowbit(w);
        return sum;
    }
}

/***************************************************************************************************************************/
/*                                                                                                                         */
/***************************************************************************************************************************/

long double f[L];
int n;
char s[L];
long double e;

pair<long double, int> k[L];
int T;

signed main() {
    rd(T); rep(_, 1, T) {
        rd(n);
        scanf("%Lf", &e);
        scanf("%s", s + 1);
        // n = strlen(s + 1);
        rep(i, 1, n) 
            f[i] = s[i] -'0', f[i] -= e;
        rep(i, 1, n) k[i] = {f[i] + k[i - 1].fir, i};
        k[n + 1] = {0, 0};
        long double der = inf;
        sort(k + 1, k + 2 + n);
        rep(i, 1, n) {
            der = min(der, abs((k[i + 1].fir - k[i].fir) / (k[i + 1].sec - k[i].sec)));
        }
        // cerr << der << endl;
        int ans = n + 1;
        const long double eps = 1e-12;
        rep(i, 1, n) {
            if(abs(der - abs((k[i + 1].fir - k[i].fir) / (k[i + 1].sec - k[i].sec))) < eps) {
                ans = min(ans, min(k[i].sec, k[i + 1].sec));
            }
        }
        cout << "Case #" << _ << ": "<< ans << endl;
    }
    return 0;
}