/*Write a program to take an input array of size n. The array should contain all the integers between 0 to n
except for one. Print that missing number*/
#include <stdio.h>
 
int main() {
    int n;
    scanf("%d", &n);
 
    int arr[n];
    int sum = 0;
 
    for (int i = 0; i < n; i++) {
        scanf("%d", &arr[i]);
        sum += arr[i];
    }
 
    int total = n * (n + 1) / 2;  // sum of 0 to n
    int missing = total - sum;
 
    printf("%d", missing);
    return 0;
}
 
 
 

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