C++ :

#include<iostream>
#include<cstring>
using namespace std;
const int N=1e3+5;
char s[N][N];
int vis[30];
int main(){
	int n,m,t;
	t=0;
	cin>>n>>m;
	for(int i=0;i<n;i++){
		cin>>s[i];
	}
	
	memset(vis,0,sizeof(vis));
	for(int i=0;i<n;i++){
		for(int j=0;j<m;j++){
			vis[s[i][j]-'A']++;
		}
	}
	int ans,num;
	ans=0;
	for(int i=0;i<28;i++){
		
		if(ans<vis[i]){
			ans=vis[i];
			num=i;
		}
	}
	
	cout<<(char)(num+'A')<<endl<<ans;
	return 0;
}

Python :

# coding=utf-8
n,m=map(int,input().split())
list1=[]
for i in range(n):
    s=input()
    list1.append(list(s))
list2=[i for j in list1 for i in j]
count_dict={}
count_dict=count_dict.fromkeys(list2)
list3=list(count_dict.keys())
for i in list3:
    count_dict[i]=list2.count(i)
count_dict=dict(sorted(count_dict.items(),key=lambda d:d[1],reverse=True))
i=0
for key,value in count_dict.items():
    if i<1:
        print(key)
        print(value)
        i+=1
        continue
    else:
        break