C++ :

#include <cstdio>
#include <iostream>
#include <string>
#include <unordered_map>
#include <cctype>
using namespace std;
int main(){
    string line;
    if(!getline(cin, line)) return 0;
    unordered_map<string, int> cnt;
    string cur;
    for(size_t i = 0; i <= line.size(); i++){
        char ch = (i < line.size()) ? line[i] : '\0';
        if(isalnum((unsigned char)ch)){
            cur.push_back((char)tolower((unsigned char)ch));   /* 统一小写 */
        }else if(!cur.empty()){
            cnt[cur]++;
            cur.clear();
        }
    }
    string bw;
    int bc = -1;
    for(unordered_map<string, int>::iterator it = cnt.begin(); it != cnt.end(); ++it){
        /* 次数多者优先；次数相同取字典序最小 */
        if(it->second > bc || (it->second == bc && it->first < bw)){
            bw = it->first;
            bc = it->second;
        }
    }
    printf("%s %d\n", bw.c_str(), bc);
    return 0;
}