#include <stdio.h>
int binsearch(int arr[], int len, int src)
{
    int idx = 0,l = 0, r = len-1;
    idx = (l + r)/2;
    while(src != arr[idx])
    {
        if(src < arr[idx])    
        {
            r = idx - 1;
        }
        else
        {
            l = idx + 1;
        }
        if(l > r)
        {
            idx = -1;
            break;
        }
        idx = (l + r)/2;
    }
    return idx;
} 
int main()
{
    int arrar[12] = {1,3,4,6,7,8,9,20,100,101,200};
    int len = 11;
    int src; 
    int result;
    scanf("%d", &src);
    result = binsearch(arrar, len, src);
    printf("Result : %d\n", result);
    return 0;
}