#include<bits/stdc++.h>
using namespace std;
using s=string;

random_device rnd;
mt19937 mt(rnd());
uniform_int_distribution<> r(0, 4);

void sum(){
    int N;
    cin >> N;
    long long Sum = 0;
    for(int i=0;i<N;i++){
        long long a;
        cin >> a;
        Sum += a;
    }

    cout << Sum << endl;
}

int FizzBuzz(){
    int A,B;
    string S;
    cin >> A >> B >> S;
    int p = r(mt);
    cout << A*(A+1)/2 << endl;
    return 0;
    if(p == 0) cout << "Hello World!" << endl;
    else if(p == 1) cout << A*(A+1)/2 << endl;
    else if(p == 2) cout << A+B << " " << S << endl;
    else {
        for(int i=1;i<=A;i++){
            if(i%15 == 0) cout << "FizzBuzz\n";
            else if(i%5 == 0) cout << "Buzz\n";
            else if(i%3 == 0) cout << "Fizz\n";
            else cout << to_string(i) + '\n';  
        }
    }
    return 0;
}


int main(){
    int p = r(mt);

    if(p < 0) sum();
    else FizzBuzz();
}