#include<stdio.h>


int binsearch( int x, int v[], int n )
{
    int low, high, mid;

    low = 0;
    high = n-1;
    mid = ( low + high )/2;

    while((low <= high) && ( v[mid] != x ))
    {
        if( x<v[mid] )
            high = mid - 1;
        else
            low = mid + 1;

        mid = ( low + high )/2;
    }

    if( x == v[mid] )
        return mid;
    else
        return -1;
}


int main()
{
     int c_in;
     int arr[] = { 1, 2, 4, 8, 16, 32 };
     
     c_in = binsearch( 8, arr, 7 );

     printf("%d\n", c_in);
    


    return 0;
}