Project Euler：Problem 47 Distinct primes factors

The first two consecutive numbers to have two distinct prime factors are:

14 = 2 × 7

15 = 3 × 5

The first three consecutive numbers to have three distinct prime factors are:

644 = 2² × 7 × 23

645 = 3 × 5 × 43

646 = 2 × 17 × 19.

Find the first four consecutive integers to have four distinct prime factors. What is the first of these numbers?

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

int factors(int n)
{
map<int, int>mp;
int i = 2;
while (n > 1)
{
if (n%i == 0)
{
mp[i]++;
n /= i;
}
else
i++;
}
return mp.size();
}

int main()
{
for (int i = 20; i <= 1000000; i++)
{
if (factors(i) == 4)
{
if (factors(i + 1) == 4)
{
if (factors(i + 2) == 4)
{
if (factors(i + 3) == 4)
{
cout << i << endl;
break;
}
}
}
}
}
system("pause");
return 0;
}