#include <bits/stdc++.h> 
int firstMissing(int arr[], int n)
{
    for(int i=0;i<n;i++){
        while (arr[i] > 0 && arr[i]<=n && arr[arr[i] - 1] != arr[i]) {
            int temp = arr[i];
            arr[i] = arr[temp - 1];
            arr[temp - 1] = temp;
        }
    }
 
    for (int i=0; i<n; ++i) {
        if (arr[i]!=i+1) {
            return i+1;
        }
    }
 
    return n+1; 
}
int main() {
	int arr[] = {3, 2, -6, 1, 0};
	    int n = sizeof(arr) / sizeof(arr[0]);
	    std::cout << "The first missing positive integer is: " << firstMissing(arr, n) << std::endl;
	    return 0;
	}

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