#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <algorithm>
#include <cmath>
#include <map>
#include <set>
#include <vector>
#include <queue>
#include <iostream>
#include <cassert>
#include <bitset>
#include <ctime>

using namespace std;

typedef long long LL;
typedef double DB;
typedef pair<int, int> PII;
typedef vector<int> VI;
typedef vector<PII> VPII;

#define X first
#define Y second
#define pb push_back
#define bit(n) (1 << (n))
#define count(n) (__builtin_popcount(n))
#define countl(n) (__builtin_popcountll(n))

template<class T>
inline void chkmin(T &x, T y) {
    if (y < x) x = y;
}

template<class T>
inline void chkmax(T &x, T y) {
    if (x < y) x = y;
}

const int MN = 100005;
const int MOD = int(1e9 + 7);
int cnt[MN][20];
char a[MN], b[MN];

int calc(char *s) {
    int n = strlen(s), i;
    int ans[20];
    memset(ans, 0, sizeof ans);
    i = 0;
    while (s[i] == '0') i++;
    int x = 0;
    for (; i < n; i++) {
        int t = s[i] - '0';
        for (int j = 0; j < t; j++) {
            for (int k = 0; k < 16; k++) {
                ans[x ^ j ^ k] = (ans[x ^ j ^ k] + cnt[n - i - 1][k]) % MOD;
            }    
        }
        x ^= t;
    }
    int rlt = 0;
    for (int i = 0; i < 16; i++) rlt = (rlt + 1LL * i * ans[i]) % MOD;
    return (rlt + x) % MOD;
}

int main() {
    
    int tn;
    
    cnt[0][0] = 1;
    for (int i = 0; i < 10; i++) cnt[1][i] = 1;
    for (int i = 2; i < MN; i++) {
        for (int j = 0; j < 10; j++) {
            for (int k = 0; k < 16; k++) {
                cnt[i][j ^ k] = (cnt[i][j ^ k] + cnt[i - 1][k]) % MOD;    
            }
        }
    }
    int T(0);
    for (cin >> tn; tn--; ) {
        scanf("%s%s", &a, &b);
        int x = 0;
        for (int i = 0; a[i]; i++) x ^= a[i] - '0';
        printf("Case #%d: %d\n", ++T, (calc(b) - calc(a) + MOD + x) % MOD);
    }
    
    return 0;
}