func_code_string: #include <bits/stdc++.h>   using namespace std;   const int N = 200005, P = 1000000007;   int n, l[N], r[N], p[N], p2[N], ans;   int power(int a, int x) {     int ans = 1;     for (; x; x >>= 1, a = 1LL * a * a % P)       if (x & 1) ans = 1LL * ans * a % P;     return ans;   }   int main() {     scanf( %d , &n);     for (int i = 1; i <= n; ++i) scanf( %d , l + i);     for (int i = 1; i <= n; ++i)       scanf( %d , r + i), p[i] = power(r[i] - l[i] + 1, P - 2);     for (int i = 1; i + 2 <= n; ++i) {       int x = max({l[i], l[i + 1], l[i + 2]}),           y = min({r[i], r[i + 1], r[i + 2]});       if (x <= y)         ans = (ans + 1LL * (y - x + 1) * p[i] % P * p[i + 1] % P * p[i + 2]) % P;     }     int sum = 0;     for (int i = 1; i + 1 <= n; ++i) {       int x = max({l[i], l[i + 1]}), y = min({r[i], r[i + 1]});       if (x <= y)         sum = (sum + (p2[i] = 1LL * (y - x + 1) * p[i] % P * p[i + 1] % P)) % P;     }     ans = 2LL * ans % P;     for (int i = 1; i + 1 <= n; ++i)       ans = (ans + 1LL * p2[i] *                        (0LL + sum - p2[i] - (i == 1 ? 0 : p2[i - 1]) -                         (i == n - 1 ? 0 : p2[i + 1]))) %             P;     ans = (ans + sum) % P;     int res = (1LL * n * n - 2LL * n * sum + ans) % P;     printf( %d n , (res + P) % P);     return 0;   }   