11661 - Burger Time?

/*
 *
 * problem link: https://onlinejudge.org/index.php?option=onlinejudge&Itemid=8&page=show_problem&category=0&problem=2708&mosmsg=Submission+received+with+ID+27781275
 *
 * */

#include <bits/stdc++.h>

using namespace std;

#define ll long long
#define endl '\n'
#define sz(x) int(x.size())
#define all(x) x.begin(), x.end()

int main() {
    ios_base::sync_with_stdio(0), cin.tie(0), cout.tie(0);

    int n;
    char s[2000005];
    while (scanf("%d", &n), n) {
        scanf("%s", s);
        int l = -1, r = -1;
        int ans = n;
        for (int i = 0; i < n; i++) {
            if (s[i] == 'Z') {
                ans = 0;
            }
            else {
                if (s[i] == 'R') l = i;
                else if (s[i] == 'D') r = i;
                if (~l && ~r) ans = min(ans, abs(l - r));
            }
        }
        printf("%d\n", ans);
    }

}