#include<stdio.h>

long long int mini(long long int left,long long int right)
{
    if(left>=right)
         return right;
    else
        return left;

}

long long int maxi(long long int left,long long int right)
{
    if(left<=right)
         return right;
    else
        return left;

}

int main()
{
    long long int left,right,power,mn,mx,a,b,c,d,e;
    scanf("%lld %lld %lld",&left,&right,&power);
    mn=mini(left,right);
    mx=maxi(left,right);
    a=mx-mn;
    b=a/2;
    c=a%2;
    if(c==1)
    {
        printf("Khelbo Na\n");
    }
    else
    {
        if(b<=power)
            printf("%lld\n",b);
        else
            printf("Khelbo Na\n");
    }
    return 0;
}