#include <string>

bool isValidNumber(std::string a) {
    size_t sz = a.size();
    if (sz == 0) {
        return false;
    }

    int cnt = 0;
    int last = 0;
    for (size_t i = 0; i < sz; ++i) {
        if ((a[i] == '.') || (a[i] == ',')) {
            cnt++;
            last = i;
        }
    }
    if (cnt == 0) {
        return (a[0] != '0');
    } else {
        if (cnt > 1) {
            return false;
        } else {
            if ((last == 0) || (last == sz - 1)) {
                return false;
            } else {
                return ((a[0] != '0') && (a[sz - 1] != '0'));
            }
        }
    }
}