import std.algorithm;
import std.array;
import std.conv;
import std.math;
import std.stdio;
import std.string;

int readint() {
    return readln.chomp.to!int;
}

int[] readints() {
    return readln.split.map!(to!int).array;
}

void main() {
    auto na = readints();
    int a = na[1];
    long[] xs = readints().map!(e => e.to!long)().array;

    if (xs.sum / xs.length == a && xs.sum % xs.length == 0) {
        writeln("YES");
    }
    else {
        writeln("NO");
    }
}