public static int minimumTotalCost(int[] departures, int[] returns, int minGap) {
    int res = Integer.MAX_VALUE;
    int minDeparture = Integer.MAX_VALUE;

    for (int R = minGap; R < departures.length; R++) {
        minDeparture = Math.min(minDeparture, departures[R - minGap]);
        res = Math.min(res, returns[R] + minDeparture);
    }

    return res == Integer.MAX_VALUE ? -1 : res;
}