View Compilation Error

910323_0_0_10158.cpp:4: error: `main' must return `int'
910323_0_0_10158.cpp: In function `int main(...)':
910323_0_0_10158.cpp:6: error: `x3' undeclared (first use this function)
910323_0_0_10158.cpp:6: error: (Each undeclared identifier is reported only once for each function it appears in.)
910323_0_0_10158.cpp:6: error: `x4' undeclared (first use this function)