View Compilation Error

0_0_31353652_32396.cpp:8:9: error: 'maxn' was not declared in this scope
 int pre[maxn];
         ^
0_0_31353652_32396.cpp: In function 'void dfs(int)':
0_0_31353652_32396.cpp:19:15: error: 'pre' was not declared in this scope
         if(v==pre[x]) continue;
               ^
0_0_31353652_32396.cpp:22:13: error: 'pre' was not declared in this scope
             pre[v]=x;
             ^
0_0_31353652_32396.cpp:32:19: error: 'pre' was not declared in this scope
                 t=pre[t];
                   ^