题解 | #剩下的树#

//土尔逊Torson 编写于2023/4/5
#define _CRT_SECURE_NO_WARNINGS
#include <cstdio>
#include <stdlib.h>

int main()
{
	int L, M;
	int tree[10001];
	while (scanf("%d%d", &L, &M) != EOF)
	{
		for (int i = 0; i <= L; ++i) {
			tree[i] = 1;
		}

		int left, right;
		for (int idx = 0; idx < M; ++idx)
		{
			scanf("%d%d", &left, &right);
			for (left; left <= right; ++left) {
				tree[left] = 0;
			}
		}

		int total = 0;
		for (int j = 0; j <= L; ++j) {
			if (tree[j] == 1) {
				++total;
			}
		}
		printf("%d\n", total);
	}
	system("pause");
	return EXIT_SUCCESS;
}
// 64 位输出请用 printf("%lld")