View Compilation Error

0_0_9878447_21016.cpp: In function `int main()':
0_0_9878447_21016.cpp:13: error: `num_1' undeclared (first use this function)
0_0_9878447_21016.cpp:13: error: (Each undeclared identifier is reported only once for each function it appears in.)
0_0_9878447_21016.cpp:13: error: `num_2' undeclared (first use this function)