import std;

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