import 'dart:io$\text{'}$; int evaluatePrefix$($String expression$)\{$ List stack $=[]$; $//$ Traverse the expression from right to left for $($int i $=$ expression.length $-1$; i $>=0$; i$--)\{$ String char $=$ expression$[$i$]$; if $($RegExp$($r$\text{'}[0-9]\text{'}).$hasMatch$($char$))\{//$ Push operands onto the stack stack.add$($int$.$parse$($char$))$; $\}$ else if $(\text{'}+*/-\text{'}.$contains$($char$))\{//$ Pop two operands for evaluation int operand$1=$ stack.removeLast$()$; int operand$2=$ stack.removeLast$()$; int result $=0$; switch $($char$)\{$ case $\text{'}+\text{'}$: result $=$ operand$1+$ operand$2$; break; case $\text{'}-\text{'}$: result $=$ operand$1-$ operand$2$; break; case $\text{'}*\text{'}$: result $=$ operand$1*$ operand$2$; break; case $\text{'}/\text{'}$: result $=$ operand$1$ ~$/$ operand$2$; $//$ Integer division break; $\}//$ Push the result back onto the stack stack.add$($result$)$; $\}\}//$ The result is the last remaining value on the stack return stack.last; $\}$ void main$()\{$ String? input $=$ stdin.readLineSync$()$; if $($input $!=$ null && input.isNotEmpty$)\{$ print$($evaluatePrefix$($input$))$; $\}\}$