Description

Saruman the White must lead his army along a straight path from Isengard to Helm’s Deep. To keep track of his forces, Saruman distributes seeing stones, known as palantirs, among the troops. Each palantir has a maximum effective range of R units, and must be carried by some troop in the army (i.e., palantirs are not allowed to “free float” in mid-air). Help Saruman take control of Middle Earth by determining the minimum number of palantirs needed for Saruman to ensure that each of his minions is within R units of some palantir.

Input

The input test file will contain multiple cases. Each test case begins with a single line containing an integer R, the maximum effective range of all palantirs (where 0 ≤ R ≤ 1000), and an integer n, the number of troops in Saruman’s army (where 1 ≤ n ≤ 1000). The next line contains n integers, indicating the positions x1, …, xn of each troop (where 0 ≤ xi ≤ 1000). The end-of-file is marked by a test case with R = n = −1.

Output

For each test case, print a single integer indicating the minimum number of palantirs needed.

Sample Input

0 3
10 20 20
10 7
70 30 1 7 15 20 50
-1 -1

Sample Output

2
4

Solution

1. 以a[0]为左端点，找满足a[i]>a[0]+r的第一个a[i],找到后以a[i-1]画圆。
2. 然后找到满足a[i-1]+r 3. 重复上述步骤，直到j=n。

Code

  1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24  #include #include #include #include using namespace std; #define N 1010 int a[N]; int main( ) { int r, n,j=1; memset(a, -1, sizeof(a)); while (scanf("%d%d", &r, &n) && r != -1 && n != -1) { for (int i = 0; i scanf("%d", &a[i]); sort(a, a + n); int ans = 0; int j = 0; while (jint temp = a[j]; while (a[j] - temp 1]; while (a[j] - temp printf("%d\n", ans); } return 0; }