#include<iostream>
#include<cstdio>
#include<cmath>
#include<ctime>
#include<queue>
#include<algorithm>
#include<cstring>
using namespace std;
#define duke(i,a,n) for(int i = a;i <= n;i++)
#define lv(i,a,n) for(int i = a;i >= n;i--)
#define clean(a) memset(a,0,sizeof(a))
const int INF = 1 << 30;
typedef long long ll;
typedef double db;
template <class T>
void read(T &x)
{char c;bool op = 0;while(c = getchar(), c < '0' || c > '9')if(c == '-') op = 1;x = c - '0';while(c = getchar(), c >= '0' && c <= '9')x = x * 10 + c - '0';if(op) x = -x;
}
template <class T>
void write(T x)
{if(x < 0) putchar('-'), x = -x;if(x >= 10) write(x / 10);putchar('0' + x % 10);
}
struct node
{int l,r,nxt;
}a[300010];
int lst[200010],len = 1,cnt = 0;
void add(int x,int y)
{a[++len].l = x;a[len].r = y;a[len].nxt = lst[x];lst[x] = len;
}
int n,m,low[200010],dfn[200010];
int from[200010],col[200010];
int du[200010];
int vis[200010];
int top = 0,st[100010],tot = 0;
void tarjan(int u,int g)
{bool flag = 0;vis[u] = 1;st[++top] = u;low[u] = dfn[u] = ++cnt;for(int k = lst[u];k;k = a[k].nxt){int y = a[k].r;if(y == g && !flag){flag = 1;continue;}if(!dfn[y]){tarjan(y,u);low[u] = min(low[u],low[y]);}else if(vis[y])low[u] = min(low[u],dfn[y]);}if(low[u] == dfn[u]){int p = 0;tot++;do{p = st[top--];col[p] = tot;vis[p] = 0;}while(p != u);}
}
int main()
{read(n);read(m);duke(i,1,m){int x,y;read(x);read(y);add(x,y);add(y,x);}duke(i,1,n)if(!dfn[i])tarjan(i,0);int ans = 0;duke(i,1,n){for(int k = lst[i];k;k = a[k].nxt){int x = a[k].l;int y = a[k].r;if(col[x] != col[y]){du[col[x]]++;du[col[y]]++;}}}
//    for(int i = 1; i <= tot; ++i) printf("%d ", du[i]); puts("")duke(i,1,tot)if(du[i] == 2)ans++;if(tot == 1)printf("0\n");elseprintf("%d\n",(ans + 1) / 2);return 0;
}