View Compilation Error

0_0_7489237_21397.cpp: In function `int main()':
0_0_7489237_21397.cpp:9: error: `ac' undeclared (first use this function)
0_0_7489237_21397.cpp:9: error: (Each undeclared identifier is reported only once for each function it appears in.)
0_0_7489237_21397.cpp:17: error: expected `}' at end of input