process.stdin.resume();
process.stdin.setEncoding('utf-8');
 
let inputString = '';
let currentLine = 0;
 
process.stdin.on('data', inputStdin => {
    inputString += inputStdin;
});
 
process.stdin.on('end', _ => {
    inputString = inputString.trim().split('\n').map(string => {
        return string.trim();
    });
    
    main();    
});
 
function readLine() {
    return inputString[currentLine++];
}

function main() {
    const num = Number(readLine())
    console.log(num >= 30 ? 'Yes' : 'No')
}