View Compilation Error

0_0_11007742_2853.cpp: In function `int main()':
0_0_11007742_2853.cpp:16: error: `abs' undeclared (first use this function)
0_0_11007742_2853.cpp:16: error: (Each undeclared identifier is reported only once for each function it appears in.)
0_0_11007742_2853.cpp: In function `int main()':
0_0_11007742_2853.cpp:27: error: redefinition of `int main()'
0_0_11007742_2853.cpp:4: error: `int main()' previously defined here
0_0_11007742_2853.cpp:39: error: `abs' undeclared (first use this function)