Compilare: user.cpp: In function ‘void back(int)’: user.cpp:20:185: warning: operation on ‘mat[6][4]’ may be undefined [-Wsequence-point] mat[1][2] = mat[1][4] = mat[1][6] = mat[2][3] = mat[2][5] = mat[2][6] = mat[3][1] = mat[3][5] = mat[4][2] = mat[4][3] = mat[4][5] = mat[5][1] = mat[5][6] = mat[6][4] = mat[6][4] = 49; ^