View Compilation Error

0_0_1649070_12286.cpp: In function `int main()':
0_0_1649070_12286.cpp:8: error: `cin' undeclared (first use this function)
0_0_1649070_12286.cpp:8: error: (Each undeclared identifier is reported only once for each function it appears in.)
0_0_1649070_12286.cpp:13: error: `p' undeclared (first use this function)
0_0_1649070_12286.cpp:16: error: `ch' undeclared (first use this function)
0_0_1649070_12286.cpp:16: error: `Graham_scan' undeclared (first use this function)
0_0_1649070_12286.cpp:22: error: `find_result' undeclared (first use this function)
0_0_1649070_12286.cpp:23: error: `printf' undeclared (first use this function)
0_0_1649070_12286.cpp:24: error: `cout' undeclared (first use this function)
0_0_1649070_12286.cpp:24: error: `endl' undeclared (first use this function)