View Compilation Error

0_0_3004343_22195.cpp: In function `int calc(int, int)':
0_0_3004343_22195.cpp:25: error: `sort' undeclared (first use this function)
0_0_3004343_22195.cpp:25: error: (Each undeclared identifier is reported only once for each function it appears in.)
0_0_3004343_22195.cpp: In function `int main(int, char**)':
0_0_3004343_22195.cpp:70: error: `cin' undeclared (first use this function)
0_0_3004343_22195.cpp:79: error: `cout' undeclared (first use this function)
0_0_3004343_22195.cpp:79: error: `endl' undeclared (first use this function)