Planning is a key to everything. As you should have understood, you can not spontaneously change the cross border plan: if you have been going to pass mountains, then please, stick to a plan, and let the luck be with you.
By the by, the mountains passage is the longest way to cross the border, so you should be sure that your group has enough supplies, otherwise human losses are inevitable.
MREs, preserves, toasts and grits are your allies against the hunger. A MRE is enough for a person to make it through three days! If only we could buy them at give-away...
Among provision you can find a roast chicken and boiled eggs, please, keep in mind that their expiration date is just a day.
That is why it is important to count necessary supplies before group's departure, remembering that food can spoil. The second piece of advice is not take food at the border checkpoint, it can go wrong.