Umnožak, I zadatak

/* Napišite program koji omogućava unos prirodnih brojeva n i preko tast. te izračunava umnožak:

S=(n+m)*(n-2*m)*(n+3*m)....)n+(-1)^(m+1)*m*m)

Poštujte sve faze procesa program.

1. dijagram toka:
https://scontent-vie1-1.xx.fbcdn.net/hphotos-xpt1/v/t34.0-12/12270528_10153162997776674_638816648_n.jpg?oh=3d6374cdff6f60712ba5cd4886356536&oe=565287BA

2. analiza i specifikacija / 3. dizajn:
https://scontent-vie1-1.xx.fbcdn.net/hphotos-xtf1/v/t34.0-12/12273099_10153162999966674_1871213227_n.jpg?oh=603ce88e0614ca4c9cd73b4b342a4629&oe=5652EE80

*/

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

int main()
{
    int suma = 1;
    int n, m;

    cout << "Unesite n (prirodan broj): ";
    cin >> n; // n=abs(n); pretvara negativan broj u pozitivan

    cout << "Unesite m (prirodan broj): ";
    cin >> m; //m=abs(m); pretvara negativan broj u pozitivan

    while (n <= 0)
    {
        cout << "Niste unijeli prirodan broj! Ponovite unos: " << endl;
        cout << "Unesite n: ";
        cin >> n;
    }

    while (m <= 0)
    {
        cout << "Niste unijeli prirodan broj! Ponovite unos: " << endl;
        cout << "Unesite m: ";
        cin >> m;
    }

    for (int i = 1; i <= m; i++)
    {
        if (n % 2 == 0)
            suma = suma*(n - (i*m));
        else
            suma = suma*(n + (i*m));
    }
    cout << "Suma je: " << suma << endl;
    system("PAUSE");
    return 0;
}