#include <stdio.h>
#include <stdlib.h>
 
// binary_search関数の実装
int binary_search(int a[], int n, int x) {
    int left = 0;
    int right = n - 1;
 
    while (left <= right) {
        int mid = left + (right - left) / 2;
 
        if (a[mid] == x) {
            return mid; // 値が見つかった場合、そのインデックスを返す
        }
        if (a[mid] < x) {
            left = mid + 1; // 探している値が右側にある場合
        } else {
            right = mid - 1; // 探している値が左側にある場合
        }
    }
    return -1; // 値が見つからない場合
}
 
int main(void) {
    int n, x, i;
    int *a;
    int ans = -1;
 
    scanf("%d %d", &n, &x);
    a = (int *)malloc(sizeof(int) * n);
    if (a == NULL) {
        printf("ERROR\n");
        return -1;
    }
    for (i = 0; i < n; i++) {
        scanf("%d", &a[i]);
    }
    ans = binary_search(a, n, x);
    if (ans != -1)
        printf("a[%d] = %d\n", ans, a[ans]);
    else
        printf("not found\n");
    free(a);
    return 0;
}

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