#include <stdio.h>
#include <stdlib.h>

int main()
{
    int v[] = {2, 3, 5, 7, 9, 12, 34, 56, 86, 93, 204, 643, 754, 856, 865};
    int n;
    n = sizeof(v)/sizeof(v[0]);
    int lo, hi,mid;
    lo = 0;
    hi = n;

    while (lo <= hi)
    {
        mid = lo + (hi-lo)/2;
        if (v[mid] == 204)
        {
           printf("%d\n", mid);
           break;
        }
        else if (v[mid] < 204) lo = mid+1;
        else hi = mid - 1;
    }
}