The directed weighted graph is given. Find the shortest distance from one vertex to another.

Input

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.

Output

Print the shortest distance from s to f or -1 if the path does not exist.