View Compilation Error

0_0_4219648_20703.cpp: In function `void unite(int, int)':
0_0_4219648_20703.cpp:19: error: `max' undeclared (first use this function)
0_0_4219648_20703.cpp:19: error: (Each undeclared identifier is reported only once for each function it appears in.)
0_0_4219648_20703.cpp: In function `int main()':
0_0_4219648_20703.cpp:28: error: `max' undeclared (first use this function)
0_0_4219648_20703.cpp:36: error: `a' undeclared (first use this function)
0_0_4219648_20703.cpp:36: error: `b' undeclared (first use this function)