Problema di Eulero 2

Il secondo problema del Progetto Eulero e' cosi' formulato

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Each new term in the Fibonacci sequence is generated by adding the previous two terms. By starting with 1 and 2, the first 10 terms will be:

1, 2, 3, 5, 8, 13, 21, 34, 55, 89, ...

By considering the terms in the Fibonacci sequence whose values do not exceed four million, find the sum of the even-valued terms.
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Il programma per il calcolo e' il seguente con soluzione 4613732
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#include <iostream>
#include <cstdlib>

using namespace std;

int main()
{
    int fibo_1 = 0;
    int fibo_2 = 1;
    int fibo = 0;
    int contatore = 1;
    int somma = 0;

    for (fibo = 1; fibo<4000000;fibo++)
    {
      fibo = fibo_1 + fibo_2;
      fibo_2 = fibo_1;
      fibo_1 = fibo;
      contatore++;
      cout << fibo << endl;
      if ((fibo%2)==0){
                            somma = somma + fibo;
                            //cout << "Pari " << contatore%2 << " " << fibo << " " << somma << endl;
                            }
      }

cout << "Somma " << somma << endl;
system("PAUSE");
return EXIT_SUCCESS;
}