#include<stdio.h>
#include<iostream>
using namespace std;

int f (int i) {
    return (i >= 34785) ? 1 : 0;
}

int binary_search() {
    /* We know that f() is a monotonic function, namely that 
       if i < j then f(i) <= f(j)

       The goal is to find the smallest index i in the range [0,1000000]
       such that f(i) = 1.  I there is no index in that range with f(i)=1
       then return -1.
    */
    
    int lo, hi, m;

    lo = 0;
    hi = 1000000;
    if (f(hi) == 0) return -1;
    if (f(lo) == 1) return lo;
    /* Induction hypothesis at start of loop: 
       lo < hi and f(lo) = 0, f(hi) = 1 */
    while(lo + 1 < hi) {
	m = lo + (hi-lo)/2;
	    /* alternative is (lo+hi)/2, but possible overflow */
	if (f(m) == 0) lo = m; else hi = m;
    }
    return hi;
}

int main() {
    printf ("%d\n", binary_search());
    return 0;
}