Largest Prime Factor Problem & Solution

#pragma GCC optimize("Ofast")
#pragma GCC optimization("unroll-loops")

#include <iostream>

using namespace std;

static const int _=[](){ios::sync_with_stdio(false);cin.tie(nullptr);cout.tie(nullptr);return 0;}();

int main() {
  long n = 600851475143;

  int result = 0;
  int i = 2;
  while (n > 1) {
    while (n % i == 0) {
      n /= i;
      result = max(result, i);
    }

    ++i;
  }

  cout << result << endl;
}