func_code_string: #include <bits/stdc++.h>   using namespace std;   int n, l[200000 + 5], r[200000 + 5];   int p[200000 + 5], q[200000 + 5], sum;   long long add(long long a, long long b) { return (a + b) % 1000000007; }   long long mul(long long a, long long b) { return 1LL * a * b % 1000000007; }   long long dec(long long a, long long b) {     return (a - b + 1000000007) % 1000000007;   }   int fst_pow(int a, int b) {     int res = 1;     while (b) {       if (b & 1) res = mul(res, a);       a = mul(a, a);       b >>= 1;     }     return res;   }   int val(int i) {     int ans = 1;     ans = dec(ans, p[i]), ans = dec(ans, p[i + 1]);     int L = max(l[i - 1], max(l[i], l[i + 1])),         R = min(r[i - 1], min(r[i], r[i + 1]));     if (L < R)       ans = add(ans, mul(R - L, fst_pow(mul(mul(r[i] - l[i], r[i - 1] - l[i - 1]),                                             r[i + 1] - l[i + 1]),                                         1000000007 - 2)));     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]);       r[i]++;     }     int sum = 0;     for (int i = 1; i <= n; i++) {       int L = max(l[i], l[i - 1]), R = min(r[i], r[i - 1]);       if (L < R)         p[i] = mul(R - L, fst_pow(mul(r[i] - l[i], r[i - 1] - l[i - 1]),                                   1000000007 - 2));       q[i] = dec(1, p[i]);       sum = add(sum, q[i]);     }     int ans = 0;     for (int i = 1; i <= n; i++) {       ans = add(ans, q[i]);       int ps = dec(sum, q[i]);       if (i > 2) ans = add(ans, val(i - 1)), ps = dec(ps, q[i - 1]);       if (i < n) ans = add(ans, val(i)), ps = dec(ps, q[i + 1]);       ans = add(ans, mul(q[i], ps));     }     printf( %d , ans);   }   