Help me in solving ENCMSG problem

help
,
1

My issue

My code

#include <iostream>
#include<string.h>
using namespace std;

int main() {
	// your code goes herest
	int a;
	cin>>a;
	while(a--){
	    int b;
	    cin>>b;
	    string s;
	    cin>>s;
	    for(int i=0;i<b;i+=2){
	        swap(s[i],s[i+1]);
	    }
	    for(int i=0;i<26;i++){
	        char ch=s[i];
	        int c=ch;
	        if(c+122-i==219){
	            c=122-i;
	            ch=c;
	        }
	        s[i]=ch;
	    }
	    cout<<s<<endl;
	}
	
	
	
	return 0;
}

Problem Link: ENCMSG Problem - CodeChef