#write a program that reads one integer and finds
#the sum 1+2+3+...+input_integer
#for example, if the input is 5
#the programs outputs: 1+2+3+4+5=15
#input = 10
#1+2+3+..+10 = 55
#1+2+..+n = (n*(n+1)/2)

def main():

	n = int(input("enter integer "))
	sum = 0
	counter = 1
	while(counter<=n):
		sum = sum + counter
		counter=counter+1

	print("sum of numbers between 1 and ", n, "is", sum)
main()