#include <algorithm>
#include <cctype>
#include <string>
#include <vector>

bool isIPv4Address(const std::string& inputString)
{
    std::vector<std::string> parts;
    std::string cur;
    for (char c : inputString) {
        if (c == '.') {
            parts.push_back(cur);
            cur.clear();
        } else {
            cur += c;
        }
    }
    parts.push_back(cur);

    for (const auto& v : parts) {
        if (v.empty() || !std::all_of(v.begin(), v.end(), [](unsigned char c) { return std::isdigit(c); })) {
            return false;
        }
        if (v.size() > 1 && v[0] == '0') {
            return false; // rejects leading zeros, mirrors $v !== (string)(int)$v
        }
        if (std::stol(v) > 255) {
            return false;
        }
    }

    return parts.size() == 4;
}