#pragma GCC optimize(2)

#pragma GCC optimize(3)

#pragma GCC optimize(4)

#include<bits/stdc++.h>

using namespace std;

#define y1 y11

#define fi first

#define se second

#define pi acos(-1.0)

#define LL long long

//#define mp make_pair

#define pb emplace_back

#define ls rt<<1, l, m

#define rs rt<<1|1, m+1, r

#define ULL unsigned LL

#define pll pair<LL, LL>

#define pli pair<LL, int>

#define pii pair<int, int>

#define piii pair<pii, int>

#define pdd pair<double, double>

#define mem(a, b) memset(a, b, sizeof(a))

#define debug(x) cerr << #x << " = " << x << "\n";

#define fio ios::sync_with_stdio(false);cin.tie(0);cout.tie(0);

//head

const int N = ;

double A[N][N];

void Gauss(int n) {

    for(int i = ; i < n; i ++) {

        int r = i;

        for(int j = i + ; j < n; j ++)

            if(fabs(A[j][i]) > fabs(A[r][i])) r = j;

        if(r != i) for(int j = ; j <= n; j ++) swap(A[r][j], A[i][j]);

        for(int j = n; j >= i; j --) {

            for(int k = i + ; k < n; k ++)

                A[k][j] -= A[k][i] / A[i][i] * A[i][j];

        }

    }

    for(int i = n - ; i >= ; i --) {

        for(int j = i + ; j < n; j ++)

            A[i][n] -= A[j][n] * A[i][j];

        A[i][n] /= A[i][i];

    }

}

int T, n, a, b, to[];

int main() {

    scanf("%d", &T);

    for(int cs = ; cs <= T; ++cs) {

        scanf("%d", &n);

        for (int i = ; i <= ; ++i) to[i] = ;

        for (int i = ; i <= n; ++i) scanf("%d %d", &a, &b), to[a] = b;

        for (int i = ; i <= ; ++i) for (int j = ; j <= ; ++j) A[i][j] = ;

        for (int i = ; i <= ; ++i) {

            A[i-][i-] = ;

            if(to[i]) {

                A[i-][to[i]-] = -;

            }

            else {

                int x = min(, -i);

                for (int j = ; j <= x; ++j) {

                    A[i-][i+j-] = -1.0/x;

                }

                if(i < ) A[i-][] = 6.0/x;

            }

        }

        Gauss();

        printf("Case %d: %.10f\n", cs, A[][]);

    }

    return ;

}