题意很简单，但是周长并比面积并又稍微麻烦了一些
这时候要开一个numseg存储竖边的个数。
再开lbd,rbd分别表示边界，这样是为了帮助删除重合的边
/*
ID: sdj22251
PROG: subset
LANG: C++
*/
#include <iostream>
#include <vector>
#include <list>
#include <map>
#include <set>
#include <deque>
#include <queue>
#include <stack>
#include <bitset>
#include <algorithm>
#include <functional>
#include <numeric>
#include <utility>
#include <sstream>
#include <iomanip>
#include <cstdio>
#include <cmath>
#include <cstdlib>
#include <cctype>
#include <string>
#include <cstring>
#include <cmath>
#include <ctime>
#define MAXN 22222
#define MAXM 104444
#define INF 100000000
#define eps 1e-7
#define L(X) X<<1
#define R(X) X<<1|1
using namespace std;
struct Seg
{int l, r, h, s;Seg(){}Seg(int a, int b, int c, int d){l = a; r = b; h = c; s = d;}bool operator <(const Seg &cmp) const{if(h == cmp.h) return s > cmp.s;return h < cmp.h;}
}seg[MAXN];
struct node
{int left, right, mid;int len, cnt, numseg;bool lbd, rbd;
}tree[4 * MAXN];
void up(int C)
{if(tree[C].cnt){tree[C].lbd = tree[C].rbd = 1;tree[C].len = tree[C].right - tree[C].left + 1;tree[C].numseg = 2;}else if(tree[C].left == tree[C].right)tree[C].len = tree[C].numseg = tree[C].lbd = tree[C].rbd = 0;else{tree[C].lbd = tree[L(C)].lbd;tree[C].rbd = tree[R(C)].rbd;tree[C].len = tree[L(C)].len + tree[R(C)].len;tree[C].numseg = tree[L(C)].numseg + tree[R(C)].numseg;if(tree[R(C)].lbd && tree[L(C)].rbd) tree[C].numseg -= 2;}
}
void make_tree(int s, int e, int C)
{tree[C].left = s;tree[C].right = e;tree[C].mid = (s + e) >> 1;tree[C].len = tree[C].cnt = tree[C].numseg = 0;tree[C].lbd = tree[C].rbd = 0;if(s == e) return;make_tree(s, tree[C].mid, L(C));make_tree(tree[C].mid + 1, e, R(C));
}
void update(int s, int e, int v, int C)
{if(tree[C].left >= s && tree[C].right <= e){tree[C].cnt += v;up(C);return;}if(tree[C].mid >= s) update(s, e, v, L(C));if(tree[C].mid < e) update(s, e, v, R(C));up(C);
}
int main()
{int n;scanf("%d", &n);int low = 10000;int high = -10000;int m = 0;for(int i = 0; i < n; i++){int a, b, c, d;scanf("%d%d%d%d", &a, &b, &c, &d);low = min(low, a);high = max(high, c);seg[m++] = Seg(a, c, b, 1);seg[m++] = Seg(a, c, d, -1);}sort(seg, seg + m);int res = 0, last = 0;make_tree(low, high, 1);for(int i = 0; i < m; i++){if(seg[i].l < seg[i].r) update(seg[i].l, seg[i].r - 1, seg[i].s, 1);if(i < m - 1) res += tree[1].numseg * (seg[i + 1].h - seg[i].h);res += abs(tree[1].len - last);last = tree[1].len;}printf("%d\n", res);return 0;
}