C语言（18分）：
#include <stdio.h>
int isPrime(int num) {
for (int i = 2; i <= num / 2; i++) {
if (num % i == 0) {
return 0;
}
}
return 1;
}
int main()
{
int N;
scanf("%d", &N);
int count = 0;
int temp = 2;
for (int i = 2; i <= N; i++) {
if (isPrime(i)) {
if (i - temp == 2) {
count++;
}
temp = i;
}
}
printf("%d", count);
return 0;
}
Java语言（18分）：
import java.util.Scanner;
public class Main {
public static void main(String[] args) {
Scanner sc = new Scanner(System.in);
int n = sc.nextInt();
int count = 0;
int temp = 2;
for (int i = 2; i <= n; i++) {
if (isPrime(i)) {
if (i - temp == 2) {
count++;
}
temp = i;
}
}
System.out.print(count);
}
public static boolean isPrime(int num) {
for (int i = 2; i <= num; i++) {
if (num % i == 0) {
return false;
}
}
return true;
}
}
