View Compilation Error

0_0_13821947_1055.c: In function 'main':
0_0_13821947_1055.c:23:21: error: 'c' undeclared (first use in this function)
      if(a==0&&b==0&&c==0)
                     ^
0_0_13821947_1055.c:23:21: note: each undeclared identifier is reported only once for each function it appears in