'use strict';

function main(stdin) {
  const loses = stdin.split('').map(s => s === 'x' ? 1 : 0);

  if (loses.filter(s => s).length > 7) {
    console.log('NO');
  } else {
    console.log('YES');
  }  
}

main(require('fs').readFileSync('/dev/stdin', 'utf8'));