#include <stdio.h>
 
void modify(int *arr, int size) {
    int *ptr = arr + size - 1;
    while (ptr >= arr) {
        *ptr = (*ptr) * (*ptr) - *(arr + (ptr - arr) / 2);
        ptr--;
    }
}
 
int main() {
    int arr[5] = {1, 2, 3, 4, 5};
    modify(arr, 5);
    int *p = arr;
    int sum = 0;
    for (int i = 0; i < 5; i++) {
        sum += *(p++);
        if (i % 2 == 0) {
            sum -= arr[i/2];
        }
    }
    printf("%d\n", sum);
    return 0;
}

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