View Compilation Error

0_0_33131227_24886.cpp: In function 'void build(int, int, int)':
0_0_33131227_24886.cpp:53:24: error: 'a' was not declared in this scope
         tree[u]={l,r,1,a[l],a[l],-1};
                        ^
0_0_33131227_24886.cpp:53:16: error: no match for 'operator=' (operand types are 'node' and '<brace-enclosed initializer list>')
         tree[u]={l,r,1,a[l],a[l],-1};
                ^
0_0_33131227_24886.cpp:53:16: note: candidates are:
0_0_33131227_24886.cpp:13:8: note: node& node::operator=(const node&)
 struct node{
        ^
0_0_33131227_24886.cpp:13:8: note:   no known conversion for argument 1 from '<brace-enclosed initializer list>' to 'const node&'
0_0_33131227_24886.cpp:13:8: note: node& node::operator=(node&&)
0_0_33131227_24886.cpp:13:8: note:   no known conversion for argument 1 from '<brace-enclosed initializer list>' to 'node&&'