#include <cstdio>
using namespace std;
const int N = 100005;
int v[N], ch[N][2], fa[N];
int rev[N];
int root, tot;
void LeftRotate(int x) {
	int y = ch[x][1], z = fa[x];
	ch[x][1] = ch[y][0];
	if (ch[x][1] != 0) {
		fa[ch[x][1]] = x;
	}
	fa[y] = z;
	if (z != 0) {
		if (ch[z][0] == x) {
			ch[z][0] = y;
		} else {
			ch[z][1] = y;
		}
	}
	fa[x] = y;
	ch[y][0] = x;
}
void RightRotate(int x) {
	int y = ch[x][0], z = fa[x];
	ch[x][0] = ch[y][1];
	if (ch[y][1] != 0) {
		fa[ch[y][1]] = x;
	}
	fa[y] = z;
	if (z != 0) {
		if (ch[z][0] == x) {
			ch[z][0] = y;
		} else {
			ch[z][1] = y;
		}
	}
	fa[x] = y;
	ch[y][1] = x;
}
void Rotate(int x) {
	if (ch[fa[x]][0] == x) {
		RightRotate(fa[x]);
	} else {
		LeftRotate(fa[x]);
	}
}
void Splay(int x, int goal_father = 0) {
	while (fa[x] != goal_father) {
		int y = fa[x];
		int z = fa[y];
		if (z != goal_father) {
			if ((ch[y][0] == x && ch[z][0] == y) || (ch[y][1] == x && ch[z][1] == y)) {
				Rotate(y);
			} else {
				Rotate(x);
			}
		}
		Rotate(x);
	}
	if (goal_father == 0) {
		root = x;
	}
}
int Find(int x) {
	int p = root;
	while (true) {
		if (v[p] == x) {
			return p;
		} else if (x < v[p]) {
			p = ch[p][0];
		} else {
			p = ch[p][1];
		}
	}
}
void Insert(int x) {
	if (root == 0) {
		tot++;
		v[tot] = x;
		root = tot;
	} else {
		int cur = root, f = 0;
		while (true) {
			if (v[cur] == x) {
				break;
			}
			f = cur;
			if (x < v[cur]) {
				if (ch[cur][0] == 0) {
					tot++;
					v[tot] = x;
					fa[tot] = f;
					ch[f][0] = tot;
					cur = tot;
					break;
				} else {
					cur = ch[cur][0];
				}
			} else {
				if (ch[cur][1] == 0) {
					tot++;
					v[tot] = x;
					fa[tot] = f;
					ch[f][1] = tot;
					cur = tot;
					break;
				} else {
					cur = ch[cur][1];
				}
			}
		}
		Splay(cur);
	}
}
int build(int l, int r, int f) {
	if (l > r) {
		return 0;
	}
	int p = ++tot;
	int mid = (l + r) / 2;
	fa[p] = f;
	v[p] = mid;
	ch[p][0] = build(l, mid - 1, p);
	ch[p][1] = build(mid + 1, r, p);
	return p;
}
void swap(int & a, int & b) {
	a ^= b ^= a ^= b;
}
int n;
void print(int p = root) {
	if (rev[p] == 1) {
		rev[p] ^= 1;
		swap(ch[p][0], ch[p][1]);
		rev[ch[p][0]] ^= 1;
		rev[ch[p][1]] ^= 1;
	}
	if (ch[p][0] != 0) {
		print(ch[p][0]);
	}
	if (p != 0 && v[p] != 0 && v[p] != n + 1) {
		printf("%d ", v[p]);
	}
	if (ch[p][1] != 0) {
		print(ch[p][1]);
	}
}
int main() {
	int m;
	scanf("%d %d", &n, &m);
	root = build(0, n + 1, 0);
	for (int l, r, i = 1; i <= m; i++) {
		scanf("%d %d", &l, &r);
		Splay(Find(l - 1), 0);
		Splay(Find(r + 1), root);
		rev[ch[ch[root][1]][0]] ^= 1;
	}
	print();
	return 0;
}

样例过了，WA 成 0 分。