The directed weighted graph is given. Find the shortest distance from one vertex to another.
The first line contains three integers n,s and f (1≤n≤2000;1≤s,f≤n), where n is the number of graph vertices, s is the initial vertex, and f is the final vertex. Each of the next n lines contains n integers — the matrix of weights of the graph, where −1 means the lack of edge between the vertices, and any nonnegative integer — the weight of the existing edge. The main diagonal of the matrix contains zeroes.
Print the shortest distance from s to f or −1 if the path does not exist.