#include<bits/stdc++.h>
#define fi first
#define se second
using namespace std;
const int N=5e5;
const int INF=1e9+7;
vector<int> e[N+10];
bool t[N+10];
int sum[N+10];
pair<int,bool> dp0[N+10];
int dp1[N+10][2];
int all[N+10];
int deg[N+10];
multiset<int> mn[N+10][2];
bool is_all(int x)
{
return all[x]==deg[x] && t[x];
}
void dfs1(int x,int p)
{
deg[x]=0;
for(auto v:e[x])
{
if(v!=p)
{
deg[x]++;
dfs1(v,x);
}
}
all[x]=0;
sum[x]=0;
dp0[x]={0,0};
for(auto v:e[x])
{
if(v==p)
continue;
if(!is_all(v))
{
sum[x]+=dp0[v].se;
dp0[x].fi+=dp0[v].fi;
sum[x]++;
}
else
all[x]++;
}
sum[x]++;
if(sum[x]%2==t[x])
{
dp0[x].se=1;
sum[x]++;
}
dp0[x].fi+=sum[x];
mn[x][0].clear();
mn[x][1].clear();
mn[x][0].insert(0);
mn[x][1].insert(INF);
for(auto v:e[x])
{
if(v==p)
continue;
if(!is_all(v))
{
mn[x][0].insert(dp1[v][!dp0[v].se]-2*dp0[v].se-dp0[v].fi);
mn[x][1].insert(dp1[v][dp0[v].se]-dp0[v].fi);
}
}
dp1[x][dp0[x].se]=dp0[x].fi+*mn[x][0].begin();
dp1[x][!dp0[x].se]=dp0[x].fi+*mn[x][1].begin()-2*dp0[x].se;
return;
}
void reroot(int nw,int old)
{
// update old root
deg[old]--;
if(!is_all(nw))
{
dp0[old].fi-=dp0[nw].se+dp0[nw].fi+1;
sum[old]-=dp0[nw].se+1;
mn[old][0].erase(mn[old][0].find(dp1[nw][!dp0[nw].se]-2*dp0[nw].se-dp0[nw].fi));
mn[old][1].erase(mn[old][1].find(dp1[nw][dp0[nw].se]-dp0[nw].fi));
}
else
all[old]--;
if(sum[old]%2==t[old])
{
dp0[old].fi-=dp0[old].se;
sum[old]-=dp0[old].se;
dp0[old].se=!dp0[old].se;
dp0[old].fi+=dp0[old].se;
sum[old]+=dp0[old].se;
}
dp1[old][dp0[old].se]=dp0[old].fi+*mn[old][0].begin();
dp1[old][!dp0[old].se]=dp0[old].fi+*mn[old][1].begin()-2*dp0[old].se;
// update new root
deg[nw]++;
if(!is_all(old))
{
dp0[nw].fi+=dp0[old].se+dp0[old].fi+1;
sum[nw]+=dp0[old].se+1;
mn[nw][0].insert(dp1[old][!dp0[old].se]-2*dp0[old].se-dp0[old].fi);
mn[nw][1].insert(dp1[old][dp0[old].se]-dp0[old].fi);
}
else
all[nw]++;
if(sum[nw]%2==t[nw])
{
dp0[nw].fi-=dp0[nw].se;
sum[nw]-=dp0[nw].se;
dp0[nw].se=!dp0[nw].se;
dp0[nw].fi+=dp0[nw].se;
sum[nw]+=dp0[nw].se;
}
dp1[nw][dp0[nw].se]=dp0[nw].fi+*mn[nw][0].begin();
dp1[nw][!dp0[nw].se]=dp0[nw].fi+*mn[nw][1].begin()-2*dp0[nw].se;
return;
}
int dfs2(int x,int p)
{
int ans=dp1[x][0];
for(auto v:e[x])
{
if(v!=p)
{
reroot(v,x);
ans=min(ans,dfs2(v,x));
reroot(x,v);
}
}
return ans;
}
int main()
{
ios_base::sync_with_stdio(false);
cin.tie(NULL);
cout.tie(NULL);
int n;
cin>>n;
for(int i=1;i<=n;i++)
{
char c;
cin>>c;
t[i]=(c=='1');
}
for(int i=1;i<n;i++)
{
int a,b;
cin>>a>>b;
e[a].push_back(b);
e[b].push_back(a);
}
dfs1(1,0);
cout<<dfs2(1,0)<<"\n";
return 0;
}
