#include <stdio.h>

int main() {
	int data[6] = {2, 4, 6, 8, 10, 12};
	int num = 5;
	int low,high,mid;
	low = 0;
	high = sizeof(data)/sizeof(int) - 1;
    
    while(low <= high){
        mid = (low + high) / 2;
        if(num > data[mid-1] && num < data[mid+1]){
            printf("%d ",mid);
            return 0;
        }
    
    else if(num > data[mid]){
        low = mid + 1;
    }
    else if(num < data[mid]){
        high = mid - 1;
    }
    }
    
	return 0;
}