#include <iostream>
using namespace std;
 
template<class T>
T sum_of_n (T n) {
  T total = 0;
  for (T i = 1; i <= n; ++i) total += i;
  return total;
}
 
unsigned int sum_of_n_formula(unsigned int n) {
	return n * (n + 1) / 2;
}
 
int main() {
	// no overflow
	cout << sum_of_n<unsigned int>(1000) << endl;
	cout << sum_of_n<int>(1000) << endl;
	cout << sum_of_n_formula(1000) << endl;
	// overflow
	cout << sum_of_n<unsigned int>(1000000000) << endl;
	cout << sum_of_n<int>(1000000000) << endl;
	cout << sum_of_n_formula(1000000000) << endl;
	return 0;
}

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