View Compilation Error

0_0_12892434_19027.cpp:3:18: stdlib: No such file or directory
0_0_12892434_19027.cpp: In function `int main()':
0_0_12892434_19027.cpp:18: error: `a' undeclared (first use this function)
0_0_12892434_19027.cpp:18: error: (Each undeclared identifier is reported only once for each function it appears in.)