#include <iostream>
#include <string>
using namespace std;

bool isValidExponentialNumber(const string& input) {
    bool hasE = false;
    bool hasDot = false;
    bool hasDigit = false;

    for (char ch : input) {
        if (ch == 'e' || ch == 'E') {
            // Check if 'e' occurs more than once or it's the first character
            if (hasE || !hasDigit) {
                return false;
            }
            hasE = true;
            hasDot = true; // Disallow dots after 'e'
        } else if (ch == '.') {
            // Check if '.' occurs more than once or after 'e'
            if (hasDot || hasE) {
                return false;
            }
            hasDot = true;
        } else if (ch == '+' || ch == '-') {
            // Only allow '+' or '-' right after 'e'
            if (hasE && input.find(ch, input.find('e')) == string::npos) {
                return false;
            }
        } else if (isdigit(ch)) {
            hasDigit = true;
        } else {
            // Invalid character
            return false;
        }
    }

    // The input is valid if it contains at least one digit
    return hasDigit;
}

int main() {
    string input;
    cout << "Enter a potential exponential number: ";
    cin >> input;

    if (isValidExponentialNumber(input)) {
        cout << "Valid exponential number." << endl;
    } else {
        cout << "Invalid exponential number." << endl;
    }

    return 0;
}