View Compilation Error

290286_0_14550.cpp: In function `int main()':
290286_0_14550.cpp:9: error: `ifstream' undeclared (first use this function)
290286_0_14550.cpp:9: error: (Each undeclared identifier is reported only once for each function it appears in.)
290286_0_14550.cpp:9: error: expected `;' before "cin"
290286_0_14550.cpp:18: error: `maxSum2' undeclared (first use this function)
290286_0_14550.cpp: In function `int maxSum2(int)':
290286_0_14550.cpp:41: error: `int maxSum2(int)' used prior to declaration