View Compilation Error

0_0_1579621_5140.cpp: In function `int main()':
0_0_1579621_5140.cpp:11: error: `n' undeclared (first use this function)
0_0_1579621_5140.cpp:11: error: (Each undeclared identifier is reported only once for each function it appears in.)
0_0_1579621_5140.cpp:13: error: `a' undeclared (first use this function)