'use strict';

function main(input) {
    const lines = input.split('\n');
    lines.pop();
    const numberOfElements = parseInt(lines[0], 10);
    const array = lines[1].split(' ').map(x => {
          return parseInt(x, 10);
        });
    console.log(fn(array));
}

function fn(raw) {
    let c = 0;
    raw.sort((a, b) => {
          if (a > b) {
                  c++
                }
        });
    if (c < 4) {
          return 'YES';
        }
    return 'NO';
}

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