第九个测试点WA 我自己测试时答案好像没问题啊

#define _CRT_SECURE_NO_WARNINGS 1
#include <stdio.h>

int main()
{
	int l, m, a[10001], b[101][2], s = 0;
	scanf("%d %d", &l, &m);
	for (int i = 1; i <= m; i++)
	{
		for (int j = 1; j <= 2; j++)
		{
			scanf("%d", &b[i][j]);
		}
		for (int p = b[i][1]; p <= b[i][2]; p++)
		{
			a[p] = 1;
		}
	}
	for (int q = 0; q <= l; q++)
	{
		if (a[q] == 1)
			s++;
	}
	int k = l + 1 - s;
	printf("%d", k);
	return 0;
}