View Compilation Error

0_0_10802948_9493.cpp: In function `int main()':
0_0_10802948_9493.cpp:14: error: `acs' undeclared (first use this function)
0_0_10802948_9493.cpp:14: error: (Each undeclared identifier is reported only once for each function it appears in.)
0_0_10802948_9493.cpp: In function `int acs(int, int)':
0_0_10802948_9493.cpp:22: error: `int acs(int, int)' used prior to declaration