View Compilation Error

0_0_3022490_31139.cpp: In function `long long int BFS()':
0_0_3022490_31139.cpp:21: error: `queue' undeclared (first use this function)
0_0_3022490_31139.cpp:21: error: (Each undeclared identifier is reported only once for each function it appears in.)
0_0_3022490_31139.cpp:21: error: expected primary-expression before '>' token
0_0_3022490_31139.cpp:21: error: `Q' undeclared (first use this function)