poj 2379 Sum of Consecutive Prime Numbers

#define _CRT_SECURE_NO_DEPRECATE
#include<iostream>
#include<algorithm>
using namespace std;
const int N_MAX = 10000 + 4;
int prime[N_MAX],res;
bool is_prime[N_MAX+1],what;
int sieve(int n) {
    int p = 0;
    for (int i = 0; i <= n; i++)is_prime[i] = true;
    is_prime[0] = is_prime[1] = false;
    for (int i = 2; i <= n; i++) {
        if (is_prime[i]) {
            prime[p++] = i;
            for (int j = i*i; j <= n; j += i)is_prime[j] = false;
        }
    }
    return  p;
}
int main() {
    int n=sieve(N_MAX),a;
    while (scanf("%d",&a)&&a) {
        res = 0,what = 0;
        int l= 0, r= 0, sum = 0;
        int bound=upper_bound(prime, prime + n, a)-prime;
        while (1) {////////
            for (;;) {////
                while (r < bound&&sum < a) {
                    sum += prime[r++];
                }
                if (sum == a) {
                    res++;
                    what = 1;
                    break;
                }
                if (sum < a) {//找不到了，终止搜索；
                    what = 0;
                    break;
                }
                sum -= prime[l++];
            }////
            if (what) { l++; r = l; sum = 0; }
            else break;
        }////////
        printf("%d\n", res);
    }
    return 0;
}