View Compilation Error

0_0_17355076_32636.cpp: In function 'bool is_triangle(int, int, int)':
0_0_17355076_32636.cpp:9:17: error: 'sum' was not declared in this scope
     return !h[a*sum + b] && a && b && c && a+b>c && a+c>b && b+c>a &&(h[a*sum+b] = true);
                 ^