import std;

void main() {
    auto K = readln.split[0].to!int;
    auto AB = readln.split.to!(int[]);
    auto A = AB[0], B = AB[1];
    
    if (B - A + 1 >= K) writeln("OK");
    else if (A%K > B%K) writeln("OK");
    else writeln("NG");
}
