View Compilation Error

0_0_4849092_15148.cpp:2: error: `main' must return `int'
0_0_4849092_15148.cpp: In function `int main(...)':
0_0_4849092_15148.cpp:4: error: `scanf' undeclared (first use this function)
0_0_4849092_15148.cpp:4: error: (Each undeclared identifier is reported only once for each function it appears in.)
0_0_4849092_15148.cpp:4: error: `EOF' undeclared (first use this function)
0_0_4849092_15148.cpp:16: error: `pow' undeclared (first use this function)
0_0_4849092_15148.cpp:17: error: `fun' undeclared (first use this function)
0_0_4849092_15148.cpp:21: error: `printf' undeclared (first use this function)
0_0_4849092_15148.cpp: In function `int fun(int)':
0_0_4849092_15148.cpp:29: error: `int fun(int)' used prior to declaration
0_0_4849092_15148.cpp:33: error: `sqrt' undeclared (first use this function)