显示代码纯文本
#include<bits/stdc++.h>
#define rep(x,y,z) for(int x=y;x<=z;x++)
#define drep(x,y,z) for(int x=y;x>=z;x--)
#define ull unsigned long long
#define ll long long
using namespace std;
inline int read()
{
int x=0;bool flag=1;char ch=getchar();
while(ch<'0'||ch>'9') {if(ch=='-')flag=0;ch=getchar();}
while(ch>='0'&&ch<='9') {x=(x<<3)+(x<<1)+ch-'0';ch=getchar();}
if(flag) return x;
return ~(x-1);
}
inline void write(int x)
{
if(x<0) {x=~(x-1);putchar('-');}
if(x>9) write(x/10);
putchar(x%10+'0');
}
/////////////////////////
const int N=2e5+50;
int ioo[31000000];
ll nc;
struct G
{
int ar;
int nx;
}a[N<<1];
int aj;
int hd[N];
inline void ADD(int x,int y)
{
a[++aj].ar=y;
a[aj].nx=hd[x];
hd[x]=aj;
}
ll ans;
ll b[2];
ll dfs(int cl,int fa,int dep)
{
b[dep]++;
dep^=1;
ll sum=1;
for(int i=hd[cl];i;i=a[i].nx)
{
if(a[i].ar==fa) continue;
sum+=dfs(a[i].ar,cl,dep);
}
ans+=sum*(nc-sum);
return sum;
}
int main()
{
freopen("Sergeyas.in","r",stdin);
freopen("Sergeyas.out","w",stdout);
nc=read();
int s1,s2;
rep(i,2,nc)
{
s1=read(),s2=read();
ADD(s1,s2);
ADD(s2,s1);
}
dfs(1,1,0);
ans>>=1;
ans+=((b[1]*b[0])>>1)+((b[1]*b[0])&1);
cout<<ans<<endl;
return 0;
}