Segmentation Fault after assignment statement(lex and yacc) - c

Question

This code works perfectly fine. After compiling lex and yacc, the code is able to do basic arithmetic operations, and even echoes the value of a variable when asked to do so. The only problem is with assignment statements.
If I want to, say, do A = 12, and later type A to see its value, the program crashes and I get a segmentation fault. How do I ensure that my assignment statements work, and how can I avoid this segmentation fault?
Here is my code:
//lex file
/*Lex input specification*/
%{
#include <stdlib.h>
#include <stdio.h>
#include "y.tab.h"
void yyerror(char*);
%}
%%
" " ;
[A-Z] { yylval = *yytext-'a'; return VARIABLE;}
[0-9]+([0-9])* { yylval=atoi(yytext); return INTEGER;}
[-/+()=*\n] { return *yytext;}
[\t] ;
. { yyerror("invalid character");}
%%
int yywrap(void) { return 1;}
And the yacc file:
/*yacc*/
%token INTEGER VARIABLE
%left '|'
%left '&'
%left '+' '-'
%left '*' '/'
%left UMINUS
%{
void yyerror(char*);
int yylex(void);
int sym[26];
#include <stdio.h>
#include <string.h>
#include <stdlib.h>
%}
%%
program:
program statement '\n'
|
;
statement:
expr {printf("%d\n",$1);}
| VARIABLE '=' expr {sym[$1] = $3;}
;
expr:
INTEGER {$$ = $1;}
| VARIABLE {$$ = sym[$1];}
| expr '*' expr {$$ = $1 * $3;}
| expr '/' expr {$$ = $1 / $3;}
| expr '+' expr {$$ = $1 + $3;}
| expr '-' expr {$$ = $1 - $3;}
| '(' expr ')' {$$ = $2;}
;
%%
void yyerror(char*s) {
fprintf(stderr, "%s\n", s);
}
int main(void) {
yyparse();
return 0;
}

Answer 1

(I flagged this as "not reproducible" because the fix was so trivial; however the flag has now timed-out/aged away. I'll answer instead so it is not shown as an open unanswered question).
As #BLUEPIXY noted:
maybe *yytext-'A'
Which, to clarify, is the lex rule:
[A-Z] { yylval = *yytext-'A'; return VARIABLE;}