UVa 11661 - Burger Time? (linear scan)

Link:https://uva.onlinejudge.org/index.php?option=com_onlinejudge&Itemid=8&category=78&page=show_problem&problem=2708
Sol:

#include <iostream>
	#include <string>
	#include <algorithm>
	using namespace std;
	int main()
	{
	int L;
	while (cin >> L, L != 0)
	{
	string S;
	cin >> S;
	int minDistance = L;
	int lastR = -L, lastD = -L;
	// Linearly scan the highway.
	for (int i = 0; i < L; ++i)
	{
	// Restaurant and drugstore.
	if (S[i] == 'Z')
	{
	minDistance = 0;
	break;
	}
	// Restaurant.
	else if (S[i] == 'R')
	{
	minDistance = min(minDistance, i - lastD);
	lastR = i;
	}
	// Drugstore.
	else if (S[i] == 'D')
	{
	minDistance = min(minDistance, i - lastR);
	lastD = i;
	}
	}
	cout << minDistance << endl;
	}
	return 0;
	}