func_code_string: #include <bits/stdc++.h>   using namespace std;   template <typename T>   void read(T &x) {     x = 0;     bool f = 0;     char c = getchar();     for (; !isdigit(c); c = getchar())       if (c ==  - ) f = 1;     for (; isdigit(c); c = getchar()) x = x * 10 + (c ^ 48);     if (f) x = -x;   }   template <typename F>   inline void write(F x, char ed =   n ) {     static short st[30];     short tp = 0;     if (x < 0) putchar( - ), x = -x;     do st[++tp] = x % 10, x /= 10;     while (x);     while (tp) putchar( 0  | st[tp--]);     putchar(ed);   }   template <typename T>   inline void write(T *st, int n, string s =   ) {     if (s.size()) cout << s <<  :  ;     while (n--) write(*st++,    );     puts(  );   }   const int N = 200050;   const int P = 1e9 + 7;   long long len[N], p[N], sum[N], ans;   int L[N], R[N], n;   long long fpw(long long x, long long mi, long long res = 1) {     for (; mi; mi >>= 1, x = x * x % P)       if (mi & 1) res = res * x % P;     return res;   }   int main() {     read(n);     for (int i = 1; i <= n; ++i) read(L[i]);     for (int i = 1; i <= n; ++i) read(R[i]), len[i] = R[i] - L[i] + 1;     long long ans = p[0] = 1;     len[0] = 1;     sum[0] = 1;     for (int i = 1; i < n; ++i) {       p[i] = max(0, min(R[i], R[i + 1]) - max(L[i], L[i + 1]) + 1);       p[i] = p[i] * fpw(len[i] * len[i + 1] % P, P - 2) % P,       p[i] = (P + 1 - p[i]) % P;       ans = (ans + p[i] + (i > 1 ? 2 * p[i] * sum[i - 2] : 0)) % P,       sum[i] = (sum[i - 1] + p[i]) % P;       int tr = min(min(R[i], R[i + 1]), R[i - 1]),           tl = max(max(L[i], L[i + 1]), L[i - 1]);       int t = max(tr - tl + 1, 0) *               fpw(len[i - 1] * len[i] % P * len[i + 1] % P, P - 2) % P;       t = (1ll - (1 - p[i - 1] + 1 - p[i]) + t) % P;       ans = (ans + 2 * t) % P;     }     write((ans % P + P) % P);     return 0;   }   