View Compilation Error

672155_0_0_3557.cpp:4: error: `main' must return `int'
672155_0_0_3557.cpp: In function `int main(...)':
672155_0_0_3557.cpp:45: error: `system' undeclared (first use this function)
672155_0_0_3557.cpp:45: error: (Each undeclared identifier is reported only once for each function it appears in.)