YAPTCHA

Time Limit: 10000/5000 MS (Java/Others)    Memory Limit: 32768/32768 K (Java/Others)
Total Submission(s): 930    Accepted Submission(s): 491

Problem Description The math department has been having problems lately. Due to immense amount of unsolicited automated programs which were crawling across their pages, they decided to put Yet-Another-Public-Turing-Test-to-Tell-Computers-and-Humans-Apart on their webpages. In short, to get access to their scientific papers, one have to prove yourself eligible and worthy, i.e. solve a mathematic riddle.


However, the test turned out difficult for some math PhD students and even for some professors. Therefore, the math department wants to write a helper program which solves this task (it is not irrational, as they are going to make money on selling the program).

The task that is presented to anyone visiting the start page of the math department is as follows: given a natural n, compute

where [x] denotes the largest integer not greater than x.   Input The first line contains the number of queries t (t <= 10^6). Each query consist of one natural number n (1 <= n <= 10^6).   Output For each n given in the input output the value of Sn.   Sample Input 13 1 2 3 4 5 6 7 8 9 10 100 1000 10000   Sample Output 0 1 1 2 2 2 2 3 3 4 28 207 1609   Source Central European Programming Contest 2008 Recommend lcy  

 1 #include
 2 #include
 3 #include
 4 #include
 5 #include
 6 using namespace std;
 7 int t;
 8 bool check[3000010];
 9 int num[1000010];
10 void Eratosthenes(){
11     check[0]=1;
12     check[1]=1;
13     for(int i=2;i<=sqrt(3000010);i++)
14         if(!check[i])
15             for(int j=2*i;j<=3000010;j+=i) check[j]=1;
16 }
17 int main(){
18     scanf("%d",&t);
19     Eratosthenes();
20     for(int i=1;i<=1000000;i++)
21         if(check[3*i+7]) num[i]=num[i-1];
22         else num[i]=num[i-1]+1;
23     int a;
24     for(int i=1;i<=t;i++){
25         scanf("%d",&a);
26         printf("%d\n",num[a]);
27     }
28     return 0;
29 }