#include <iostream>

using namespace std;


int binsearch(int* a, int val, int lo, int hi) {
    if (hi < lo) return -1;
    int mid = (lo+hi)/2;
    if (val < a[mid]) {
        return binsearch(a, val, lo, mid-1);
    } else if (val > a[mid]) {
        return binsearch(a, val, mid+1, hi);
    } else {
        return lo;
    }
}

int main(void) {
    int a[10] = {0,1,2,3,4,5,6,7,8,9};
    int lo = 0;
    int hi = 9;

    int val = 3;

    cout << binsearch(a, val, lo, hi) << endl;
}