function main(input) {
    const args = input.split(' ');
    const a = parseInt(args[0], 10);
    const b = parseInt(args[1], 10);
    const c = parseInt(args[2], 10);
    const d = parseInt(args[4], 10);

    const takahashi = Math.floor( c/b ) + 1;
    const aoki      = Math.floor( a/d ) + 1;

    if( takahashi <= aoki ){
      console.log('Yes');
    }else{
      console.log('No');
    }
}

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