Algorithm
A triangular number is the number of dots in an equilateral triangle uniformly filled with dots. For example, three dots can be arranged in a triangle; thus three is a triangular number. The n-th triangular number is the number of dots in a triangle with n dots on a side. 
. You can learn more about these numbers from Wikipedia (http://en.wikipedia.org/wiki/Triangular_number).
Your task is to find out if a given integer is a triangular number.
The first line contains the single number n (1 ≤ n ≤ 500) — the given integer.
If the given integer is a triangular number output YES, otherwise output NO.
1
YES
2
NO
3
YES
Code Examples
#1 Code Example with C++ Programming
Code -
C++ Programming
#include <iostream>
using namespace std;
int main() {
int n, c = 1;
cin >> n;
for(int i = 1; c <= n; i++, c += i)
if(c == n) {
cout << "YES" << endl;
return 0;
}
cout << "NO" << endl;
return 0;
}Input
Output
Demonstration
Codeforcess Solution Triangular numbers ,A. Triangular numbers C,C++, Java, Js and Python ,A. Triangular numbers,Codeforcess Solution