process.stdin.resume();
process.stdin.setEncoding('ascii');

var input_stdin = "";
var input_stdin_array = "";
var input_currentline = 0;

process.stdin.on('data', function (data) {
    input_stdin += data;
});

process.stdin.on('end', function () {
    input_stdin_array = input_stdin.split("\n");
    main();    
});

function readLine() {
    return input_stdin_array[input_currentline++];
}

/////////////// ignore above this line ////////////////////

function main() {
    var n = parseInt(readLine());
    m = readLine().split(' ');
    m = m.map(Number);
    // your code goes here
    var modulo = function (x) { return x%1000000007; };
    var permutations = function (x) {
        var r = 3;
        var z = x;
        while (x > 1) {
            r += z - x--;
        }
        return (r);
    };
    
    if (n < 3) { console.log(1); }
    else { console.log( permutations(n) );
    }

}