1 #include <bits/stdc++.h>
 2 #define INF 0x3f3f3f3f
 3 #define LL long long
 4 using namespace std;
 5 const int MAXN = 1e6+10;
 6 const LL mod = 1e9+7;
 7 LL fac[MAXN], Inv[MAXN];
 8
 9 namespace IO{
10     const int MAX = 4e7;
11     char buf[MAX]; int c, sz;           //预先缓冲到数组buf
12     void begin(){
13         c = 0;
14         sz = fread(buf, 1, MAX, stdin);
15     }
16     inline bool read(int &t){
17         while(c < sz && buf[c] != '-' && (buf[c] < '0' || buf[c] > '9')) c++;
18         if(c >= sz) return false;
19         bool flag = 0; if(buf[c] == '-') flag = 1, c++;
20         for(t = 0; c < sz && '0' <= buf[c] && buf[c] <= '9'; c++) t = t*10+buf[c]-'0';
21         if(flag) t=-t;
22         return true;
23     }
24 }
25
26 void Init()                                 //预处理排列数和逆元
27 {
28     fac[0] = Inv[0] = fac[1] = Inv[1] = 1;
29     for(int i = 2; i < MAXN; i++) fac[i] = fac[i-1]*i%mod;
30     for(int i = 2; i < MAXN; i++) Inv[i] = (mod-mod/i)*Inv[mod%i]%mod;
31     for(int i = 2; i < MAXN; i++) Inv[i] = Inv[i]*Inv[i-1]%mod;
32 }
33
34 LL C(LL n, LL m)                            //计算组合数
35 {
36     return fac[n]*Inv[m]%mod*Inv[n-m]%mod;
37 }
38
39 struct Node
40 {
41     int l, r;
42     int id;
43 }a[MAXN];
44
45 bool cmp(const Node s1, const Node s2)
46 {
47     if(s1.l == s2.l) return s1.r > s2.r;
48     return s1.l < s2.l;
49 }
50 int ii;
51 LL dfs(int L, int R)
52 {
53     if(a[ii].l != L || a[ii].r != R) return 0;
54     int mid = a[ii++].id;
55     LL fL = 1LL, fR = 1LL;
56     if(L <= mid-1) fL = dfs(L, mid-1);      //左区间方案数
57     if(R >= mid+1) fR = dfs(mid+1, R);      //右区间方案数
58     LL cc = C(R-L, mid-L);
59     return fL*fR%mod*cc%mod;
60 }
61
62 int main()
63 {
64     Init();
65     int N, Case = 1;
66     IO::begin();
67     while(IO::read(N)){
68         for(int i = 1;i <= N; i++) IO::read(a[i].l);
69         for(int i = 1;i <= N; i++) IO::read(a[i].r), a[i].id = i;
70         sort(a+1, a+1+N, cmp); ii = 1;
71         LL ans = dfs(1, N);
72         printf("Case #%d: %lld\n", Case++, ans);
73     }
74     return 0;
75 }