n=int(input())

tree=[[0,0,0]for k in range(n+1)]

tree[1][0]=1

for i in range(1,n+1):

    tree[i][0]=i
    
    temp=input().split()
    
    tree[i][1],tree[i][2]=int(temp[0]),int(temp[1])

def height(tree,node):

    if tree[node][1]==tree[node][2]==0:
    
        return 0;
        
    lh = height(tree,tree[node][1]);
    
    rh = height(tree,tree[node][2]);
    
    return max(lh,rh)+1

print(height(tree,1)+1)