View Compilation Error

0_0_2861772_19801.cpp: In function `void Add()':
0_0_2861772_19801.cpp:29: error: `strrev' undeclared (first use this function)
0_0_2861772_19801.cpp:29: error: (Each undeclared identifier is reported only once for each function it appears in.)
0_0_2861772_19801.cpp: In function `int main()':
0_0_2861772_19801.cpp:38: error: `strrev' undeclared (first use this function)