#include <stdio.h>

int main() {
    int k, a, b, c = 0;
    scanf("%d%d%d", &k, &a, &b);
    
    for (int i = a; i < b + 1; ++i)
        if (i % k == 0)
            c = 1;
    
    if (c)
        printf("OK");
    else
        printf("NG");
    
    return 0;
}