桥边数量

type edge=record
        nt,u,v:longint;
        end;
const     maxn=100008;
      maxm=200008;
var eg:array[0..maxm*2] of edge;
    lt:array[0..maxn] of longint;
    dfn,low,stack,cl:array[0..maxn] of longint;
    i,j,n,m,u,v,sum,num,k:longint;
    tmp,now:longint;
procedure add(u,v:longint);
begin
    inc(sum);
    eg[sum].u:=u;
    eg[sum].v:=v;
    eg[sum].nt:=lt[u];
    lt[u]:=sum;
end;
function min(a,b:longint):longint;
begin
    if a<b then exit(a) else exit(b);
end;
procedure dfs(u,fa:longint);
var v,i:longint;
begin
    inc(tmp); dfn[u]:=tmp; low[u]:=tmp;
    inc(now); stack[now]:=u;
    i:=lt[u];
    while i<>-1 do
    begin
        v:=eg[i].v;
        if v<>fa then
            if dfn[v]=0 then
            begin
                dfs(v,u);
                low[u]:=min(low[u],low[v]);
            end
            else low[u]:=min(low[u],dfn[v]);
        i:=eg[i].nt;
    end;
    if dfn[u]=low[u] then
    begin
        inc(num);
        while true do
        begin
            v:=stack[now];
            cl[v]:=num;
                        dec(now);
            if u=v then break;
        end;
    end;
end;
begin
    for i:=1 to maxn do lt[i]:=-1;
    readln(n,m);
    sum:=-1;
    for i:=1 to m do
    begin
        readln(u,v);
        add(u,v);
        add(v,u);
    end;
    for i:=1 to n do
        if dfn[i]=0 then
            dfs(i,0);
    for i:=1 to sum do
        if odd(i) then
        begin
            if cl[eg[i].u]<>cl[eg[i].v] then inc(k);
        end;
       writeln(k);
       //for i:=1 to n do write(cl[i],'  ');
end.