vs上正确啊，怎么在这里一个都过不了

#include<iostream>
#include<cmath>
#include<algorithm>
using namespace std;
int main()
{
    int l, m;
    cin >> l >> m;
        cout << endl;
        int p[10001],a,b;
        int j = 0;
        for (int i = 0; i <= l; i++)
            p[i] = 1;
        for (int i = 0; i < m; i++)
        {
            cin >> a>> b;
                for (int k = a; k <= b; k++)
            {
                p[k] = 0;
            }
        }
        int count=0;
        for (int t = 0; t <= l; t++)
        {
            if (p[t] !=0)
                count++;
        }
        cout << count;
    return 0;
}