用qsort时间超了怎么办

#include<stdio.h>
#include<stdlib.h>
int a[5000005];
int n, k;
int cmp(const void* a, const void* b)
{
	return *(int*)a - *(int*)b;
}
int main()
{
	scanf("%d%d", &n, &k);
	for (int i = 0; i < n; i++)
	{
		scanf("%d", &a[i]);
	}
	qsort(a, n, sizeof(int), cmp);
	printf("%d", a[k]);
	return 0;
}