1 #include<algorithm>
 2 #include<iostream>
 3 #include<cstdlib>
 4 #include<cstring>
 5 #include<cstdio>
 6 #include<vector>
 7 #include<map>
 8 using std::cin;
 9 using std::cout;
10 using std::endl;
11 using std::find;
12 using std::sort;
13 using std::map;
14 using std::pair;
15 using std::vector;
16 #define pb(e) push_back(e)
17 #define sz(c) (int)(c).size()
18 #define mp(a, b) make_pair(a, b)
19 #define all(c) (c).begin(), (c).end()
20 #define iter(c) decltype((c).begin())
21 #define cls(arr,val) memset(arr,val,sizeof(arr))
22 #define cpresent(c, e) (find(all(c), (e)) != (c).end())
23 #define rep(i, n) for (int i = 1; i <= (int)(n); i++)
24 #define tr(c, i) for (iter(c) i = (c).begin(); i != (c).end(); ++i)
25 const int N = 1010;
26 typedef unsigned long long ull;
27 struct UnionFind {
28     int par[N], rank[N];
29     inline void init(int n) {
30         rep(i, n) {
31             par[i] = i;
32             rank[i] = 0;
33         }
34     }
35     inline int find(int x) {
36         while (x != par[x]) {
37             x = par[x] = par[par[x]];
38         }
39         return x;
40     }
41     inline void unite(int x, int y) {
42         x = find(x), y = find(y);
43         if (rank[x] < rank[y]) {
44             par[x] = y;
45         } else {
46             par[y] = x;
47             if (rank[x] == rank[y]) rank[x]++;
48         }
49     }
50     inline void result(int n) {
51         int tot = 0;
52         rep(i, n) { if (par[i] == i) tot++; }
53         printf("%d\n", tot - 1);
54     }
55 }go;
56 int main() {
57 #ifdef LOCAL
58     freopen("in.txt", "r", stdin);
59     freopen("out.txt", "w+", stdout);
60 #endif
61     int n, m, a, b;
62     while (~scanf("%d", &n) && n) {
63         go.init(n);
64         scanf("%d", &m);
65         rep(i, m) scanf("%d %d", &a, &b), go.unite(a, b);
66         go.result(n);
67     }
68     return 0;
69 }