--hdu 2124 Repair the Wall(贪心)

#include<stdio.h>
#include<stdlib.h>
int cmp(const void *a,const void *b)
{
    return *(int *)b-*(int *)a;
}
int main()
{
    int L, N, i;
    int a[601], sum, len;
    while(scanf("%d",&L)!=EOF)
    {
        scanf("%d",&N);
        for(i = 0; i < N; i++)
            scanf("%d",&a[i]);
        qsort(a, N, sizeof(a[0]), cmp);
        sum = len = 0;
        for(i = 0; i < N; i++)
        {
            if(len < L)
            {
                len += a[i];
                sum++;
            }
            else
                break;
        }
        if(len < L)
            printf("impossible\n");
        else
            printf("%d\n",sum);
    }
    return 0;
}