View Compilation Error

0_0_19098844_13648.cpp:5:7: error: 'de' does not name a type
 const de[4][2]={{1,0},{-1,0},{0,1},{0,-1}};
       ^
0_0_19098844_13648.cpp: In function 'void dfs(int, int)':
0_0_19098844_13648.cpp:16:9: error: 'de' was not declared in this scope
    a1=a+de[i][0];
         ^