char_frequency.cpp

#include <bits/stdc++.h>
using namespace std;
//
#define ll long long
#define ull unsigned long long
#define mx 100010
#define mod 1000000007
#define inf INT_MAX
#define pi acos(-1)
#define endl '\n'
#define pb push_back
#define debug cout << "OK" << endl
#define fin freopen("input", "r", stdin)
#define Fast ios_base::sync_with_stdio(false);cin.tie(0);cout.tie(0)
//
int main() {
    string str;
    cin >> str;

    multimap<ll, char> m;
    multimap<ll, char>::iterator it;
    ll cnt = 1;

    for (ll i = 1; i < str.length(); i++) {
        if (str[i] == str[i - 1]) cnt++;
        else {
            m.insert({ cnt, str[i - 1] });
            cnt = 1;
        }
    }
    m.insert({ cnt, str[str.length() - 1] });
    it = m.end();
    it--;

    cout << it->second << " -> " << it->first << endl;
}