View Compilation Error

0_0_38438834_12020.cpp: In function 'bool MAIN::check(int, int, int)':
0_0_38438834_12020.cpp:12:11: error: 'i' was not declared in this scope
   if (vis[i][j][k]) {
           ^
0_0_38438834_12020.cpp:12:14: error: 'j' was not declared in this scope
   if (vis[i][j][k]) {
              ^
0_0_38438834_12020.cpp:12:17: error: 'k' was not declared in this scope
   if (vis[i][j][k]) {
                 ^