View Compilation Error

0_0_36378979_23000.cpp: In function 'void unionset(int, int, int)':
0_0_36378979_23000.cpp:22:18: error: expected ']' before ';' token
       sum[find(a);]=sum[b]-sum[a]+s;
                  ^
0_0_36378979_23000.cpp:22:19: error: expected primary-expression before ']' token
       sum[find(a);]=sum[b]-sum[a]+s;
                   ^