#include <stdio.h>
#include <stdlib.h>

int main( int argc, char *argv[] )
{
    int k, a, b;

    scanf( "%d %d %d", &k, &a, &b );

    for( int i=a; i<=b; i++ ) {
        if( i % k == 0 ) {
            puts( "OK" );
            exit( 0 );
        }
    }

    puts( "NG" );
}
