Compilare: main.cpp: In function 'bool ok(int, int, int)': main.cpp:42:84: warning: comparison of constant '-1' with boolean expression is always true [-Wbool-compare] return (x >= 1 && y >= 1 && z >= 1 && x <= n && y <= n && z <= n && a[x][y][z] != -1); ~~~~~~~~~~~^~~~~