#include <iostream>
#include <string>
#include <cctype>
#include <algorithm>
#include <iterator>
#include <array>
using namespace std;
 
int main() {
	string line, cleared_line;
	getline(cin, line);
	copy_if(begin(line), end(line), back_inserter(cleared_line), [](auto c){ return isalpha(c); });
	array<size_t, 'z'-'a'> occurs{{}};
	for(auto c : cleared_line){
		c = tolower(c);
		occurs[c-'a'] += 1;
	}
 
	auto max = max_element(begin(occurs), end(occurs));
	cout << (char)(distance(begin(occurs), max)+'a') << ": " << *max << endl;
	return 0;
}

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QWxhIG1hIGtvdGEsIGEga290IG1hIGFsZQ==

Ala ma kota, a kot ma ale