func_code_string: #include <bits/stdc++.h>   using namespace std;   int read() {     int x = 0, sgn = 1;     char ch = getchar();     for (; !isdigit(ch); ch = getchar())       if (ch ==  - ) sgn = -1;     for (; isdigit(ch); ch = getchar()) x = (x << 1) + (x << 3) + (ch ^ 48);     return x * sgn;   }   const int N = 1e5 + 10;   int n;   long long ans1, ans2;   struct line {     int x, y, l, r;   } seg[N];   bool cmp1(line a, line b) { return a.x < b.x; }   bool cmp2(line a, line b) { return a.y < b.y; }   struct BITT {     int arr[N << 1];     void add(int x, int v = 1) {       for (; x <= (n * 2); x += x & -x) arr[x] += v;       return;     }     int q(int x, int v = 0) {       for (; x; x -= x & -x) v += arr[x];       return v;     }     void clear() { memset(arr, 0, sizeof(arr)); }   } BIT;   int main() {     n = read();     for (int i = 1; i <= n; i++) seg[i].x = read(), seg[i].y = read();     for (int i = 1; i <= n; i++)       if (seg[i].x > seg[i].y) swap(seg[i].x, seg[i].y);     sort(seg + 1, seg + n + 1, cmp1);     for (int i = 1; i <= n; i++) {       seg[i].l += BIT.q(seg[i].x) + BIT.q(n << 1) - BIT.q(seg[i].y);       BIT.add(seg[i].y);     }     BIT.clear();     for (int i = n; i >= 1; i--) {       seg[i].r += BIT.q(seg[i].y);       BIT.add(seg[i].y);     }     BIT.clear();     sort(seg + 1, seg + n + 1, cmp2);     for (int i = n; i >= 1; i--) {       seg[i].l += BIT.q(n << 1) - BIT.q(seg[i].y);       BIT.add(seg[i].x);     }     ans1 = 1ll * n * (n - 1) * (n - 2) / 6;     for (int i = 1; i <= n; i++) {       ans1 -= 1ll * seg[i].l * seg[i].r;       ans2 += 1ll * (seg[i].l + seg[i].r) * (n - seg[i].l - seg[i].r - 1);     }     printf( %lld n , ans1 - ans2 / 2);     return 0;   }   