#include <cstring>
#include <cmath>
#include <cstdio>
#include <climits>
#include <ctime>
#include <cassert>
#include <cctype>
#include <iostream>
#include <algorithm>
#include <numeric>
#include <map>
#include <set>
#include <queue>
#include <string>
#include <vector>
#include <bitset>
#include <utility>

using namespace std;
#define all(x) (x).begin(), (x).end()
#define bit(x) (1 << (x))
#define cnt1(x) (__builtin_popcount(x))
#define LB lower_bound
#define LET(it,v) __typeof(v) it(v)
#define mset0(x) memset((x), 0, sizeof((x)))
#define mset1(x) memset((x), -1, sizeof((x)))
#define pb push_back
#define PQ priority_queue
#define REP(it,v) for(LET(it,v.begin());it!=v.end();it++)
#define sqr(x) ((x)*(x))
#define sz(x) ((int)(x.size()))
#define UB upper_bound
#define X first
#define Y second

typedef long long LL;
typedef double DB;
typedef pair<int, int> pii;
typedef pair<LL, LL> pll;
typedef vector<int> vi;
typedef vector<pii> vpii;

template <class T> inline void chkmin(T &a, T b) {
    if (b < a) a = b;
}
template <class T> inline void chkmax(T &a, T b) {
    if (a < b) a = b;
}

const int MX = 100005;
const int MOD = 1000000007;
char s[MX], t[MX];
int cnt[MX][17];

void add(int &a, int b) {
    a += b;
    if (a >= MOD) a -= MOD;
}

LL calc(char *s) {
    int n = strlen(s);
    LL rlt = 0;
    int cur = 0;
    
    for (int i = 0; i < n; i++) {
        int k = s[i] - '0';
        for (int j = 0; j < k; j++) {
            for (int h = 0; h < 16; h++) {
                rlt += (LL)cnt[n - i - 1][h] * (h ^ j ^ cur);
            }
            rlt %= MOD;
        }
        cur ^= k;
    }
    return rlt;
}

void init() {
    cnt[0][0] = 1;
    for (int i = 0; i < 10; i++) cnt[1][i] = 1;
    for (int i = 1; i < MX - 1; i++) {
        for (int j = 0; j < 16; j++) {
            for (int k = 0; k < 10; k++) {
                add(cnt[i + 1][k ^ j], cnt[i][j]);
            }
        }
    }
}

int main() {
    
    int T, Tc = 0;
    init();
    
    for (scanf("%d", &T), Tc = 1; T--; Tc++) {
        scanf("%s%s", s, t);
        printf("Case #%d: ", Tc);
        LL ans = calc(t) - calc(s);
        
        int cur = 0;
        for (int i = 0; t[i]; i++) cur ^= (t[i] - '0');
        ans = ((ans % MOD + MOD) + cur) % MOD;
        printf("%d\n", int(ans));
    }
    
    return 0;
}