View Compilation Error

0_0_17959754_11001.cpp: In function 'LL dfs(int, int, int, int)':
0_0_17959754_11001.cpp:21:36: error: 'i' was not declared in this scope
   if(t==0 && check(x,y) && check(x,i) && check(y,i)) ret=1;
                                    ^