process.stdin.resume();
process.stdin.setEncoding('utf8');

var lines = [];
var reader = require('readline').createInterface({
    input: process.stdin,
    output: process.stdout
});
reader.on('line', (line) => {
    // ここで入力を処理する
    lines.push(line);
});
reader.on('close', () => {
    const k = lines.slice(-1);
    lines = lines.slice(0,-1);
    const n = lines.length-1; 
    for(let i=0; i<=n; i++){
        for(let j=n-i; j>0; j--){
            if( (lines[j] - lines[i]) > k){
                console.log(":(");
                return;
            }
        }
    }
    console.log("yay!");
});