C :

#include<stdio.h>
int main()
{
	int n,i,s=0;
	scanf("%d",&n);
	for(i=1;i<=n;i++)
	{
		s=s+i;
	}
	printf("sum=%d\n",s);
}

C++ :

#include<bits/stdc++.h> 
#include<stdio.h> 
using namespace std;
int main()
{
	int sum=0;
	int n;
	cin>>n;
	for(int i=1;i<=n;++i)
	{
		sum+=i;
	}
	printf("sum=%d",sum);
	return 0;
	
}

Java :

import java.util.Scanner;

public class Main
{
	public static void main(String[] args)
	{
		Scanner sc=new Scanner(System.in);
		int a=sc.nextInt();
		int sum=0;
		for(int i=1;i<=a;i++)
		{
			sum+=i;
		}
		System.out.println("sum="+sum);

	}
}

Python :

# coding=utf-8
#!/usr/bin/python2
import sys
import re
import math


a=int(input())
sum=0
b=a+1
for i in range(1,b):
    sum=sum+i
    
    
print 'sum=%d'%(sum)

C# :

using System;
using System.Collections.Generic;
using System.Linq;
using System.Runtime.InteropServices;
using System.Security.Cryptography;
using System.Text;
using System.Threading.Tasks;

namespace ConsoleApp2
{
    internal class Program
    {
        static void Main()
        {
            int num = 0;
            int n = Convert.ToInt32(Console.ReadLine());
            for (int i = 1; i <= n; i++)
            { num += i; }
            Console.WriteLine("sum="+num); 
            Console.ReadKey();
     
        }
    }
}