View Compilation Error

0_0_29584360_13713.c: In function 'main':
0_0_29584360_13713.c:25:25: error: 'a' undeclared (first use in this function)
                     if (a[j] == -1) {
                         ^
0_0_29584360_13713.c:25:25: note: each undeclared identifier is reported only once for each function it appears in