View Compilation Error

0_0_25757244_28930.cpp: In function 'void union2(int, int)':
0_0_25757244_28930.cpp:41:23: error: lvalue required as left operand of assignment
     siz[get_fa1(fa[y])-=siz2[y];
                       ^
0_0_25757244_28930.cpp:41:32: error: expected ']' before ';' token
     siz[get_fa1(fa[y])-=siz2[y];
                                ^