#include <iostream>
#include <cstdio>
#include <algorithm>
#include <cstring>

template <class T>
inline void read(T &x) {
    x = 0;
    int f = 0;
    char ch = getchar();
    while (!isdigit(ch))    { f |= ch == '-'; ch = getchar(); }
    while (isdigit(ch))     { x = (x << 1) + (x << 3) + (ch ^ 48); ch = getchar(); }
    x = f ? -x : x;
    return;
}

int k, a, b;

int main() {
    read(k), read(a), read(b);
    for (int i = a; i <= b; ++i) {
        if (i % k == 0) {
            puts("OK");
            return 0;
        }
    }
    puts("NG");
    return 0;
}