View Compilation Error

246794_0_21547.cpp: In function `int main()':
246794_0_21547.cpp:4: error: `a' undeclared (first use this function)
246794_0_21547.cpp:4: error: (Each undeclared identifier is reported only once for each function it appears in.)
246794_0_21547.cpp:9: error: `n' undeclared (first use this function)
246794_0_21547.cpp:10: error: expected primary-expression before "int"
246794_0_21547.cpp:10: error: expected `;' before "int"
246794_0_21547.cpp:12: error: `sum' undeclared (first use this function)