process.stdin.resume();
process.stdin.setEncoding('utf8');
// 自分の得意な言語で
// Let's チャレンジ！！

var lines = [];
var reader = require('readline').createInterface({
  input: process.stdin,
  output: process.stdout
});
reader.on('line', (line) => {
  lines.push(line);
});
reader.on('close', () => {
  const readLines = (input) => input.split('\n')
  var c = (value) => console.log(value)
var x = parseInt(lines[0]);
  if(x >=30){
  	c('Yes');
  }else{
    c('No')
  }
  
});