View Compilation Error

0_0_2125186_10993.cpp:15: error: `main' must return `int'
0_0_2125186_10993.cpp: In function `int main(...)':
0_0_2125186_10993.cpp:23: error: `strrev' undeclared (first use this function)
0_0_2125186_10993.cpp:23: error: (Each undeclared identifier is reported only once for each function it appears in.)