#include <stdio.h>
int main(void) {
// 探索アルゴリズムの処理確認コード
int binary_search(int a[], int n, int key) {
int low = 0, high = n - 1;
while (low <= high) {
int mid = (low + high) / 2;
if (a[mid] == key) return mid;
if (a[mid] < key) low = mid + 1; else high = mid - 1;
}
return -1;
}
return 0;
}