B4 in LOSH 2016

import java.util.Scanner;

public class Main {
    public static void death(long x, long y, long n, long c, long mas[], long h, byte a[][]){
        long opa[] = new long[20001];
        y=x;
        for (int i = 1; i < n; i++){
            opa[i] = 0;
        }
        c = 0;
        h = 0;
        ++c;
        opa[(int)c] = x;
        while (h < c){
            ++h;
            x = opa[(int)h];
            for (int i = 0; i < n; i++){
                if (a[(int)x][i]!= 0 && (mas[i]==0) && (i !=y)){
                    ++c;
                    opa[(int)c]=i;
                    mas[i] = mas[(int)x]+1;
                }
            }
        }
    }
    public static void main(String[] args) {
        long mas[] = new long[20001];
        Scanner sc = new Scanner(System.in);
        byte a[][] = new byte[20001][20001];
        long c=0, h=0, n, k, y = 0, s, m, x1, x2, j, max=0;
        n = sc.nextLong();
        m = sc.nextLong();
        s = sc.nextLong();
        for (int i = 0; i < m; i++){
            x1 = sc.nextLong();
            x2 = sc.nextLong();
            a[(int)x2][(int)x1] = 1;
        }
        death(s,y,n,c, mas, h, a);
        max=0;
        for(int i = 0; i < n; i++){
            if (mas[i]> max){
                max = mas[i];
            }
        }
        System.out.println(max);
    }
}