r-step connection

If $P_i \rightarrow P_j$ holds, we say there is one step connection from $P_i$ to $P_j$. If $P_i \rightarrow P_k \rightarrow P_j$ holds, we say there is a two step connection from $P_i$ to $P_j$. Similarly, if $P_i \rightarrow P_{k_1} \rightarrow P_{k_2} \rightarrow \dots \rightarrow P_{k_{r-1}} \rightarrow P_j$ holds we say there is an r-step connection from $P_i$ to $P_j$. In other words, if there is a path of length r from $P_i$ to $P_j$, we say, there is an r-step connection from $P_i$ to $P_j$. Notice that we are assuming all the connections have the same unit length.
Consider the following graph

Figure 12

In the graph given above since $P_1 \rightarrow P_2$ holds,there is a one step connection from $P_1$ to $P_2$. Also, there is a one step connection from $P_3$ to $P_1$, and so on. There are 2-step connection from $P_4$ to $P_2$, $P_1$ to $P_4$, and $P_3$ to $P_2$, ...