function result $=$ solve$($N$,$ S$)$

$\%$ Initialize a frequency array for each character

frequency $=$ zeros$(26,1)$;

$\%$ Iterate through all substrings

for i $=1$:N

for j $=$ i:N

$\%$ Extract substring and update frequency array

substring $=$ S$($i:j$)$;

frequency$($substring $-\text{'}$a$\text{'}+1)=$ frequency$($substring $-\text{'}$a$\text{'}+1)+1$;

end

end

$\%$ Find the character with the maximum frequency

maxFrequency $=$ max$($frequency$)$;

maxCharIndex $=$ find$($frequency $==$ maxFrequency, $1,$ 'first'$)$;

$\%$ Convert index to character

result $=$ char$(\text{'}$a$\text{'}+$ maxCharIndex $-1)$;

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