include <stdio.h>

int main() {

int n, S;
while (scanf("%d", &n) == 1)
{
    S = 0;
    for (int i = 1; i <= n; i++)
    {
        S = S + i;
    }
    printf("%d\n",S);
}
return 0;

}

import rsa, os

if not os.path.exists('cipher/rsa/keys'):

os.makedirs('cipher/rsa/keys')

class RSACipher:

def __init__(self):
    pass

def generate_keys(self):
    (public_key, private_key) = rsa.newkeys(1024)
    with open('cipher/rsa/keys/publicKey.pem', 'wb') as p:
        p.write(public_key.save_pkcs1('PEM'))
    with open('cipher/rsa/keys/privateKey.pem', 'wb') as p:
        p.write(private_key.save_pkcs1('PEM'))

def load_keys(self):
    with open('cipher/rsa/keys/publicKey.pem', 'rb') as p:
        public_key = rsa.PublicKey.load_pkcs1(p.read())
    with open('cipher/rsa/keys/privateKey.pem', 'rb') as p:
        private_key = rsa.PrivateKey.load_pkcs1(p.read())
    return private_key, public_key

def encrypt(self, message, key):
    return rsa.encrypt(message.encode('ascii'), key)

def decrypt(self, ciphertext, key):
    try:
        return rsa.decrypt(ciphertext, key).decode('ascii')
    except:
        return False

def sign(self, message, key):
    return rsa.sign(message.encode('ascii'), key, 'SHA-1')

def verify(self, message, signature, key):
    try:
        return rsa.verify(message.encode('ascii'), signature, key,) == 'SHA-1'
    except:
        return False