#include <iostream>
using namespace std;
int calcMissing(int* input, int size)
{
int sum = 0;
int n = 1;
for(int i = 0; i < size; i++)
{
if(input[i] > 0)
{
sum += input[i];
n++;
}
}
if(sum == 0)
return 1;
return (n*(n+1)/2) - sum;
}
int main()
{
cout << calcMissing(new int[4]{3, 4, -1, 1}, 4) << endl;
cout << calcMissing(new int[3]{1, 2, 0}, 3) << endl;
cout << calcMissing(new int[1]{0}, 1) << endl;
}