1632.c

#include <stdio.h>

void _qsort(int *a, int *b, int l, int r);

int main(){
    int m, n, a[2001], b[2001], i, cur = 0, cnt = 0;
    scanf("%d%d", &m, &n);
    n <<= 1;
    for (i = 0; i < n; i += 2){
        scanf("%d%d", &a[i], &a[i + 1]);
        b[i] = 1, b[i + 1] = -1;
    }
    _qsort(a, b, 0, n - 1);
    for (i = 0; i < n; i++){
        cur += b[i];
        if (0 == cur)
            cnt++;
    }
    printf("%d\n", cnt);

    return 0;
}

void _qsort(int *a, int *b, int l, int r){
    int tmp, m, i, j;
    i = l, j = r;
    m = a[(l + r) / 2];
    do{
        while (a[i] < m)
            i++;
        while (a[j] > m)
            j--;
        if (i <= j){
            if (a[i] > a[j] || (a[i] == a[j] && b[j] == 1)){
                tmp = a[i];
                a[i] = a[j];
                a[j] = tmp;
                tmp = b[i];
                b[i] = b[j];
                b[j] = tmp;
            }
            i++;
            j--;
        }
    }while (i <= j);
    if (i < r)
        _qsort(a, b, i, r);
    if (j > l)
        _qsort(a, b, l, j);
}