#include<bits/stdc++.h>
using namespace std;
 
char *func(char*);
 
int main(){
 
	char* in = "ab$cd";
 
	char* out = "";
 
	out = func(in);
 
	printf("%s" , out);
 
	return 0;
 
}
 
char* func(char* in){
 
	//char *out = "";
	int len = strlen(in);
	int i = 0;
	int j = len - 1;
 
	while(i<j)
	{
		if(!isalpha(in[i]))
			i++;
		else if(!isalpha(in[j]))
			j--;
		else {
			swap(in[i] , in[j]);
			i++;
			j--;
		}      	
	}	
	//out = in;
 
	return in;
 
}

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