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());
    a = readLine().split(' ');
    a = a.map(Number);
    
    a.sort(function(a,b) {return a-b;});
//    console.log(a)
    var longest = -1;
    
    for (var i = 0; i < a.length-1; i++) {
        var sum = 1;
        var j = i+1;
        while (j < a.length && a[j] <= a[i]+1) {
            sum++;
            j++;
        }
        if (sum > longest) longest = sum;
    }
    console.log(longest);

}