View Compilation Error

0_0_6748709_24649.cpp: In function `int _next(int)':
0_0_6748709_24649.cpp:19: error: `ctz' undeclared (first use this function)
0_0_6748709_24649.cpp:19: error: (Each undeclared identifier is reported only once for each function it appears in.)
0_0_6748709_24649.cpp: In function `void calc(int)':
0_0_6748709_24649.cpp:34: error: `next' undeclared (first use this function)