03. Deposit Calculator

#include <iostream>

using namespace std;

int main() {
    double sum;
    cin >> sum;

    int months;
    cin >> months;

    double annualPercentage;
    cin >> annualPercentage;

    double total = sum + sum * months * annualPercentage / 1200;

    cout << total << endl;

    return 0;
}

Или леко тарикатската:)

#include <iostream>

using namespace std;

int main() {
    double sum, months, annualPercentage;
    cin >> sum >> months >> annualPercentage;

    cout << sum + sum * months * annualPercentage / 1200 << endl;

    return 0;
}