Missing Number

//computing missing number among 1 to 100
//sum of 100 natural numbers is 5050
//and removing the obtained sum from the n natural numbers
#include <cmath>
#include <cstdio>
#include <vector>
#include <iostream>
#include <algorithm>
using namespace std;


int main() {
   
    int a[100];
    int sum=0;
    int c=5050;
    for(int i=0;i<100;i++)
    {
        cin>>a[i];
        sum+=a[i];
      }
    if(sum>c)
    {
        cout<<sum-c;
     }
    else if(sum<c)
    {
        cout<<c-sum;
     }
    else
    {
        return 0;
     }
    return 0;
}