C :

#include<stdio.h>
#include<string.h>
int main()
{
	int i,j,s=0,ss=0,max=0;
	char a[200];
	gets(a);
	for(i=0;i<strlen(a);i++){
		if(a[i]!=' '&&a[i]!='.'){
			if(a[i]=='a') {
				ss=1; 
			}
			s++;
			continue;
		}
		else{
			if(ss>0&&s>max){
				max=s;
				j=i-1;
			}
			s=0;
			ss=0;
		}
	} 
	if(max==0) printf("NO");
	else{
		for(i=j-max+1;i<=j;i++){
			printf("%c",a[i]);
		}
	}
	return 0;
}

C++ :

#include <iostream>
#include <cstring>
using namespace std;

bool hasA(char s[]){
	bool f = false;
	int i;
	for (i = 0;i < strlen(s);i++){
		if (s[i] == 'a'){
			f = true;
			break;
		}
	}
	return f;
}

int main(){
	char s[2000];
	char w[2000];
	char f[2000] = "";
	gets(s);
	int i,k = 0;
	for (i = 0;s[i] != '.';i++){
		if (s[i] != ' '){
			w[k] = s[i];
			k++;
			if (s[i + 1] == '.' || s[i + 1] == ' '){
				w[k] = '\0';
				//cout<<w<<endl;
				if (hasA(w) && strlen(w) > strlen(f)){
					strcpy(f,w);
				}
				k = 0;
			}
		}
	}
	if (strlen(f) == 0){
		cout<<"NO";
	}else{
		cout<<f<<endl;
	}
}

Java :

import java.util.HashMap;
import java.util.Map;
import java.util.Scanner;
public class Main{
	public static void main(String[] args) {
		Scanner scanner=new Scanner(System.in);
		String scanStr=scanner.nextLine();
		String str=scanStr.replace(".","");
		String[] strArray=str.split(" ");
		int max_length=0;
		Map numMap=new HashMap();
		for(int i=0;i<strArray.length;i++){
			if(!"".equals(strArray[i])){
				if(strArray[i].contains("a")){
					int length=strArray[i].length();
					if(length>max_length){
						max_length=length;
						numMap.put("name", strArray[i]);
					}
				}
			}
		}
		if(max_length==0){
			System.out.println("NO");
		}else{
			System.out.println(numMap.get("name"));
		}
	}
}

Python :

str1=input()
l = str1[0:len(str1)-2].split(' ')
max=''
if 'a' not in str1:
    print('NO')
else:
    for i in l:
        if 'a' in i:
            if len(i)>len(max):
                max=i
    print(max)