C :

#include "stdio.h"


int dui[10000], num[10000];
int n, m,head,trail,sum;

void work(int x)
{
	int i;
	int number;
	sum = 0;
	head = 1;
	trail = 0;
	for (i = 0; i <= 1000; i++)
	{
		num[i] = 0;
	}
	for (i = 1; i <= x; i++)
	{
		scanf("%d", &number);
		if (num[number] == 0)
		{
			sum++;
			if (trail - head + 1 < m)
			{
				trail++;
				dui[trail] = number;
				num[number] = 1;
			}
			else
			{
				num[dui[head]] = 0;
				head++;
				trail++;
				dui[trail] = number;
				num[number] = 1;
			}
		}

	}
	printf("%d\n", sum);
}



void main()
{
	int i;
	while (scanf("%d %d", &m, &n) != EOF)
	{
		work(n);
	}
}

C++ :

#include <stdio.h>

int main ()
{
	int n, m, a[1001], dir[1001], i, j;
	while(scanf("%d%d",&m,&n) != EOF)
	{
		int l = 0, r = -1, num = 0;
		for(i = 0 ; i < n ; i ++)
		{
			scanf("%d",&a[i]);
			for(j = l ; j <= r ; j ++)
				if(a[i] == dir[j])
					break;
			if(j == r + 1)
			{
				if(r - l == m - 1)
				{
					l ++;
					r ++;
					dir[r] = a[i];
				}
				else
				{
					r ++;
					dir[r] = a[i];
					
				}
				num ++;
			}
		}
		printf("%d\n",num);
	}
	return 0;
}