#include <bits/stdc++.h>
using namespace std;
typedef long long ll;

struct Frac{
    ll p,q;
    Frac()=default;
    constexpr Frac(ll p,ll q=1):p(p),q(q){}
    bool operator<(const Frac &other)const{
        return p*other.q<other.p*q;
    }
    Frac operator*(const Frac &other)const{
        return Frac(p*other.p,q*other.q);
    }
    Frac operator-(const Frac &other)const{
        return Frac(p*other.q-other.p*q,q*other.q);
    }
};

inline Frac abs(const Frac &x){
    return Frac(abs(x.p),x.q);
}

char s[500010],t[10];
int a[500010],b[500010];
Frac v[500010];

int main(){
    int q,n,pos;Frac ans;
    ios::sync_with_stdio(false);cin.tie(nullptr);
    cin>>q;
    for(int cnt=1;cnt<=q;cnt++){
        cin>>n>>t>>s+1;pos=1e9;ans=1;
        const Frac f((t[0]-'0')*1000000
            +(t[2]-'0')*100000+(t[3]-'0')*10000
            +(t[4]-'0')*1000+(t[5]-'0')*100
            +(t[6]-'0')*10+t[7]-'0',1000000);
        for(int i=1;i<=n;i++)
            a[i]=a[i-1]+s[i]-'0',v[i]=Frac(a[i])-f*i,b[i]=i;
        sort(b,b+n+1,[&](int x,int y){return v[x]<v[y];});
        for(int i=0;i<=n;i++){
            for(int j=i+1;j<=min(i+1000,n);j++){
                const int l=min(b[i],b[j]),r=max(b[i],b[j]);
                const Frac t=abs(Frac(a[r]-a[l],r-l)-f);
                if(t<ans)ans=t,pos=l;
                else if(!(ans<t))pos=min(pos,l);
            }
        }
        cout<<"Case #"<<cnt<<": "<<pos<<'\n';
    }
    return 0;
}