6.cpp

/*
The sum of the squares of the first ten natural numbers is,

1^2 + 2^2 + ... + 10^2 = 385
The square of the sum of the first ten natural numbers is,

(1 + 2 + ... + 10)^2 = 552 = 3025
Hence the difference between the sum of the squares of the first ten natural numbers and the square of the sum is 3025 − 385 = 2640.

Find the difference between the sum of the squares of the first one hundred natural numbers and the square of the sum.
*/

#include <iostream>
//#include <cmath>
#include <vector>

using namespace std;

int main()
{
  unsigned long long sum1 = 0;
  unsigned long long sum2 = 0;
  for (int i = 1; i < 101; ++i)
  {
    cout << "i= " << i << endl;
    sum1 += i*i;
    sum2 += i;
  }

  unsigned long long result = sum2*sum2 - sum1;
  cout << "Result = " << result << endl; 
}