Lex/Yacc (shift | reduce)/reduce conflicts

%{
   #include <stdio.h>
   #include <stdlib.h>
   FILE *fp;
   char *fname;
   extern int lastentry;
%}
%token IDENTIFIER INTCONSTANT BOOLCONSTANT ASSIGNMENT NOTEQUAL LESSTHANOREQUAL
%token GREATERTHANOREQUAL WHITESPACE COMMENT INTEGER BOOLEAN BEGINN END WHILE
%token DO IF THEN READ WRITE PROGRAM
%left '+' '-'
%left '*' '/'
%%
program: PROGRAM IDENTIFIER ';' declarationlist statementlist '.'
;
declarationlist: declarationlist declaration
               |
;
declaration: type identifierlist ';'
;
identifierlist: IDENTIFIER ',' identifierlist
              |
;
type: INTEGER
    | BOOLEAN
;
statementlist: BEGINN statements END
;
statements: statements statement
          |
;
statement: assignmentstatement
         | ifstatement
         | whilestatement
         | writestatement
         | readstatement
;
assignmentstatement: IDENTIFIER ASSIGNMENT expression ';'
;
ifstatement: IF expression THEN statementlist ';'
;
whilestatement: WHILE expression DO statementlist ';'
;
writestatement: WRITE expressionlist ';'
;
readstatement: READ identifierlist ';'
;
expressionlist: expression ',' expressionlist
              |
;
expression: relation relationallist
;
relationallist: relationallist relationaloperator relation
              |
;
relationaloperator: '='
                  | NOTEQUAL
                  | '<'
                  | LESSTHANOREQUAL
                  | '>'
                  | GREATERTHANOREQUAL
;
relation: term addingoplist
;
addingoplist: addingoplist addingop term
            |
;
addingop: '+'
        | '-'
;
term: factor multioplist
;
multioplist: multioplist multiop factor
           |
;
multiop: '*'
       | '/'
;
factor: IDENTIFIER
      | INTEGER
      | expression
;
%%
int main(void)
{
   yyparse();
   return 0;
}

declarationlist: declarationlist declaration
                            | declaration
                            |

declarationlist: declarationlist declaration
                            |