C++ :

#include <bits/stdc++.h>
using namespace std;
int n,a[1000],s;
int main(){
	cin>>n;
	for (int i=0;i<n;i++){
		cin>>a[i];
		s=s+a[i]*a[i];
	}
	cout<<s;
	return 0;
}

Java :

import java.util.Scanner;
public class Main {
    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        int num1 = scanner.nextInt();
//        int num2 = scanner.nextInt();
        int[] a = new int[num1];
        int count1 = 0,count2 = 0, count3 = 0;
        int s = 0;
        for (int i = 0; i < num1; i++) {
            a[i] = scanner.nextInt();
        }
        for (int i = 0 ; i < num1; i++) {
            s = s + a[i] * a[i];
        }
        System.out.println(s);

    }

    public static boolean judge(int i,int j){
        int a,s = 0;
        while(i != 0){
            a = i % 10;
            s = s + a;
            i /= 10;
        }
        if(s == j)return true;
        else return false;
    }

    public static void paiXu(int[] a){
        int temp;
        for(int i = 0;i < a.length - 1;i++){
            for(int k = 0;k < a.length - i - 1;k++){
                if(a[k] > a[k + 1]){
                    temp = a[k];
                    a[k] = a[k + 1];
                    a[k + 1] = temp;
                }
            }
        }
    }
}

Python :

n = int(input())
a = input().split()
su = 0
for i in a:
    k = int(i)
    su += k * k
print(su)