//二分查找
int main()
{
int arr[] = {2,3,4,6,7,8,9,10};
int len = sizeof(arr) / sizeof(int);
int n;
int left = 0, right = len - 1;
int mid=0,flat=0;
int wz = 0;//记录查找数是第几个
//查找n
scanf("%d", &n);
while (left <= right) {
mid = (left + right) / 2;
if (arr[mid] > n)
{
right = mid - 1;

}
if (arr[mid] < n)
{
left = mid + 1;
}
if (arr[mid] ==n)
{
wz = mid + 1;
flat = 1;
break;
}

}
if (flat == 1)
{
printf("%d\n", wz);
}
else
{
printf("no founding");
}
}