function main(input) 
{
    input = input.split("\n");
    var number = input[1].split(" ");
    var count = 0;
    
    for (i=0; i < number.length; i++)
    {
        for (j=0; j < number.length; j++)
        {
            if (number[i] == number[j])
            {
                count++;
            }
        }
    }
    if (count > number.length)
    {
        console.log("YES");
    }
    else
    {
        console.log("NO")
    }
}
main(require('fs').readFileSync('/dev/stdin', 'utf8'));