字母的出现次数统计

#include <bits/stdc++.h>
using namespace std;
int main(){
    string a;
    getline(cin,a);
    string a1;
    map<char,int> x;
    char max1;
    int max2; 
    for(int i = 0;i<a.size();i++){
        if(a[i]>='A' && a[i]<='Z' || a[i]>='a' && a[i]<='z'){
            if(a[i]>='A' && a[i]<='Z'){
                a[i] += 32;
            }
            x[a[i]]++;
            max2 = max(x[a[i]],max2);
            if(max2==x[a[i]]){
                max1 = a[i];
            }
            a1 += a[i]; 
        }
    }
    cout<<max1<<" "<<max2;
    return 0;
}