C++ :

#include <bits/stdc++.h>
using namespace std;

int main(){
	string s;
	int i,x;
	getline(cin,s);
	int a[200] = {0};
	for(i = 0;i < s.size();i++){
		x = s[i];
		a[x]++;
	}
	
	char c;
	int max = 0;
	for(i = 'z';i >= 'a';i--){
		if(a[i] > max){
			max = a[i];
			c = i;
		}
	}
	cout<<c<<endl;
}

Java :

import java.util.Scanner;
public class Main {
    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        String c = scanner.next();
//        int num1 = scanner.nextInt();
//        String a = scanner.nextLine();
//        String b = new String();
//        String[] str = new String[2];
        int[] count = new int[27];
        for(int i = 1;i <= 26;i++){
            for (int j = 0; j < c.length(); j++) {
                if(c.charAt(j) == i+96){
                    count[i]++;
                }

            }
        }
        int max = MAX(count);
        for (int i = 26; i >= 0; i--) {
            if(max == count[i]){
                System.out.println((char)(i+96));
                break;
            }
        }




    }public static void paiXu(int[] a,int length){
        int temp;
        for(int i = 0;i < length - 1;i++){
            for(int k = 0;k < length - i - 1;k++){
                if(a[k] > a[k + 1]){
                    temp = a[k];
                    a[k] = a[k + 1];
                    a[k + 1] = temp;
                }
            }
        }
    }
    public static int er(int n)
    {
        if(n==0)
        {return 0;}
        int f1=1,f2;
        n--;
        while(n != 0)
        {
            f2=f1*2;
            f1=f2;
            n--;
        }
        return f1;
    }

    public static void paiXud(int[] a){
        int temp;
        for(int i = 0;i < a.length - 1;i++){
            for(int k = 0;k < a.length - i - 1;k++){
                if(a[k] < a[k + 1]){
                    temp = a[k];
                    a[k] = a[k + 1];
                    a[k + 1] = temp;
                }
            }
        }
    } public static void paiXux(int[] a){
        int temp;
        for(int i = 0;i < a.length - 1;i++){
            for(int k = 0;k < a.length - i - 1;k++){
                if(a[k] > a[k + 1]){
                    temp = a[k];
                    a[k] = a[k + 1];
                    a[k + 1] = temp;
                }
            }
        }
    }

    public static int MAX2(int[][] a){
        int max = a[0][0];
        for (int i = 0; i < a.length; i++) {
            for(int j = 0;j < a[0].length;j++){
                if(max < a[i][j])max = a[i][j];
            }
        }
        return max;
    }public static int MIN2(int[][] a){
        int min = a[0][0];
        for (int i = 0; i < a.length; i++) {
            for(int j = 0;j < a[0].length;j++){
                if(min > a[i][j])min = a[i][j];
            }
        }
        return min;
    }
    public static int MAX(int[] a){
        int max = a[0];
        for (int i = 0; i < a.length; i++) {
            if(max < a[i]){
                max = a[i];
            }
        }
        return max;
    }

    public static int MIN(int[] a){
        int min = a[0];
        for (int i = 0; i < a.length; i++) {
            if(min > a[i]){
               min = a[i];
            }
        }
        return min;
    }
    public static int sum(int a){
        int x,s = 0;
        while(a != 0){
            x = a % 10;
            s = s + x;
            a /= 10;
        }
        return s;
    }
    public static boolean isPrime(int a){
        if(a <= 1)return false;
        else
        for(int i = 2;i <= Math.sqrt(a);i++){
            if(a % i == 0)return false;
        }return true;
    }

    public static long qiuYu(long i){
        long a;
        a = i % 10;
        return a;
    }
    public static int daoXu(int x){
        int s = 0,m;
        while(x != 0){
            m = x % 10;
            s = s * 10 + m;
            x /= 10;
        }
        return s;
    }

    public static int jiaWei(int x){
        int s = 0,m;
        while(x != 0){
            m = x % 10;
            s = s + m;
            x /= 10;
        }
        return s;
    }

    public static int fun(int x){
        if(x == 1 || x == 2)return 1;
        else return fun(x - 1) + fun(x - 2);
    }
}

Python :

str1=input().strip()
alist = list(set(str1))
alist.sort(reverse=True)


dic1=dict()
for t in str1:
    if t not in dic1:
        dic1[t]=1
    else:
        dic1[t]=dic1[t]+1
'''
for key in dic1.keys():
    print(key,dic1[key])
'''
bb=sorted(dic1.items(), key=lambda kv: (-kv[1], -ord(kv[0])))
'''
for item in bb:
    print(item[0],item[1])
'''
print(bb[0][0])