int count = 0;
for (int n = 1000; n <= 9999; n++) {
    int a = n / 1000;
    int b = (n / 100) % 10;
    _________________________ // L1
    int d = n % 10;
    if (a * a * a * a + b * b * b * b + c * c * c * c + d * d * d * d == n) { // 特定条件
        count++;
    }
}