View Compilation Error

0_0_38105639_25441.cpp: In function 'void solve()':
0_0_38105639_25441.cpp:48:9: error: expected unqualified-id before '[' token
   auto &[a, b] = w[i];
         ^
0_0_38105639_25441.cpp:48:9: error: expected initializer before '[' token
0_0_38105639_25441.cpp:49:3: error: 'a' was not declared in this scope
   a = find(a), b = find(b);
   ^
0_0_38105639_25441.cpp:49:16: error: 'b' was not declared in this scope
   a = find(a), b = find(b);
                ^