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 maximumValue(a) {
    // Return the maximum value of f among all subsegments [l..r].
    
    for (var i = 0; i < a.length; i++) {
        for (var j = 0; j < a.length; j++) {
            var maxF = 0;
            var sum = a[i] + a[j];
            var max = Math.max(a[i], a[j]);
            
            var f = sum + max;
            
            
            if (maxF < f)
                maxF = f;
        }
    }
   return maxF;
}

function main() {
    var n = parseInt(readLine());
    a = readLine().split(' ');
    a = a.map(Number);
    var result = maximumValue(a);
    process.stdout.write("" + result + "\n");

}