<?php
 
error_reporting(-1);
mb_internal_encoding('utf-8');
 
$input = '243+6743-78*2=';
$inputLength = mb_strlen($input);
 
$number = 0;
$result = 0;
$op = '';
 
for ($i = 0; $i < $inputLength; $i++){
 
	$char = mb_substr($input, $i, 1);
	if ($char == '+' || $char == '-' || $char == '=' || $char == '*') {
		if ($op == '') {
			$result = $number;
		} elseif ($char == '=') {
			echo $result;
			exit();
		}
		$op = $char;
		$number = 0;
	} elseif (is_numeric($char)) {
		$char = intval($char);
		$number = $number*10 + $char;
	} else {
		echo "Неверный символ: '$char'\n";
	}
}
 
?>

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