I make FUll import i become this error more times.

IMP-00017: Echec de l'instruction suivante avec erreur ORACLE 6550 :
"DECLARE SREC DBMS_STATS.STATREC; BEGIN SREC.MINVAL := '4C5232'; SREC.MAXVA" "L := '564953555F4E54'; SREC.EAVS := 0; SREC.CHVALS := NULL; SREC.NOVALS := " "DBMS_STATS.NUMARRAY(396281680244272000000000000000000000,448024748093994000"
"000000000000000000); SREC.BKVALS := DBMS_STATS.NUMARRAY(0,1); SREC.EPC := 2" "; DBMS_STATS.SET_COLUMN_STATS(NULL,'"S_UTI_IMP"','"UI_NOMIMP"', NULL ,NULL,"
"NULL,4,,25,0,srec,5,0); END;"

and

IMP-00019: ligne rejetée en raison de l'erreur ORACLE 1
IMP-00003: Erreur ORACLE 1 rencontrée
ORA-00001: violation de contrainte unique (SYSTEM.HELP_TOPIC_SEQ)

How can i avoid this error in output of import?