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Q4948.java
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Q4948.java
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package forRank;
import java.io.BufferedReader;
import java.io.BufferedWriter;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.OutputStreamWriter;
import java.util.Arrays;
public class Q4948 {
private static final int N_MAX = 123456;
private static boolean primary[];
public static void main(String[] args) throws IOException {
BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
BufferedWriter bw = new BufferedWriter(new OutputStreamWriter(System.out));
primary = new boolean[2 * N_MAX + 1];
String input = null;
Arrays.fill(primary, true);
primary[1] = false;
for (int i = 2; i * i <= N_MAX * 2; i++) {
for (int j = i * 2; j <= N_MAX * 2; j += i)
primary[j] = false;
}
while(true){
input = br.readLine();
int n = Integer.parseInt(input);
if(n == 0)
break;
int cnt = 0;
for (int i = n + 1; i <= 2 * n; i++) {
if(primary[i])
cnt++;
}
bw.write(cnt + "\n");
}
br.close();
bw.close();
}
}