"use strict";
var __importStar = (this && this.__importStar) || function (mod) {
    if (mod && mod.__esModule) return mod;
    var result = {};
    if (mod != null) for (var k in mod) if (Object.hasOwnProperty.call(mod, k)) result[k] = mod[k];
    result["default"] = mod;
    return result;
};
Object.defineProperty(exports, "__esModule", { value: true });
var fs = __importStar(require("fs"));
function main(n, xn) {
    xn = xn.sort();
    for (var i = 0; i < xn.length - 1; i++) {
        if (xn[i] === xn[i + 1]) {
            console.log('NO');
            return;
        }
    }
    console.log('YES');
}
var input = fs.readFileSync("/dev/stdin", "utf8").split("\n");
var args1 = parseInt(input[0]);
var args2 = input[1].split(' ').map(function (n) { return parseInt(n); });
main(args1, args2);
