> //poj2306
> 
> #include<stdio.h>
> #define MAXN 1010
> 
> int X[MAXN];
> int R, n;
> 
> void read_data(int n);
> void solve(void);
> 
> int main(int argc, char* argv[])
> {
> 	while(scanf("%d %d", &R, &n) && R != -1)
> 	{
> 		read_data(n);
> 		solve();
> 	}
> }
> 
> void read_data(int n)
> {
> 	int temp;
> 	for(int i = 0; i < MAXN; ++i)
> 		X[i] = 0;
> 	for(int i = 0; i < n; ++i)
> 	{
> 		scanf("%d", &temp);
> 		X[temp] = 1;
> 	}
> }
> 
> void solve(void)
> {
> 	int ans = 0;
> 	int start, mid, end;
> 	for(int i = 0; i < MAXN; ++i)
> 	{
> 		if(X[i] != 0)
> 		{
> 			ans++;
> 			start = i;
> 			mid = i + R;
> 			while(X[mid] == 0) mid--;
> 			for(int j = start; j <= mid+R; j++)
> 				X[j] = 0;
> 		}
> 	}
> 	printf("%d\n", ans);
> }