#5679. CSES1723 图的路径 I
CSES1723 图的路径 I
Graph Paths I
Consider a directed graph that has n nodes and m edges. Your task is to count the number of paths from node 1 to node n with exactly k edges.
Input
The first input line contains three integers n, m and k: the number of nodes and edges, and the length of the path. The nodes are numbered 1,2,\dots,n. Then, there are m lines describing the edges. Each line contains two integers a and b: there is an edge from node a to node b.
Output
Print the number of paths modulo 10^9+7.
Constraints
Example
Input
3 4 8
1 2
2 3
3 1
3 2
Output
2
Explanation: The paths are 1 \rightarrow 2 \rightarrow 3 \rightarrow 1 \rightarrow 2 \rightarrow 3 \rightarrow 1 \rightarrow 2 \rightarrow 3 and 1 \rightarrow 2 \rightarrow 3 \rightarrow 2 \rightarrow 3 \rightarrow 2 \rightarrow 3 \rightarrow 2 \rightarrow 3.