#include <bits/stdc++.h>
#define fi first
#define se second
#define all(v) v.begin() , v.end()
#define sz(v) (int)v.size()
#define unq(v) sort(all(v)); v.resize(unique(all(v)) - v.begin());
using namespace std;

typedef long long ll;
typedef pair<int , int> ii;
typedef pair<long long , int> lli;

const int maxN = int(5e5)+7;
const int LOG = 20;

int n , q , a[maxN]; string s;
vector<int> g[maxN];
int d[maxN] , in[maxN] , out[maxN] , DfsTime = 0 , fa[maxN];
int p[maxN] , h[maxN] , sz[maxN] , numChain = 0 , numPos = 0 , chain[maxN] , pos[maxN] , head[maxN];

void dfs(int u){
    d[u] = d[p[u]] + a[u];
    in[u] = ++DfsTime;
    sz[u] = 1;
    for (int v : g[u]){
        if (v != p[u]){
            p[v] = u;
            h[v] = h[u] + 1;
            dfs(v);
            sz[u] += sz[v];
        }
    }
    out[u] = DfsTime;
}

void hld(int u){
    if (head[numChain] == 0) head[numChain] = u;
    chain[u] = numChain;
    pos[u] = ++numPos;
    int heavy = -1;
    for (int v : g[u]){
        if (v != p[u] && (heavy == -1 || sz[heavy] < sz[v])) heavy = v;
    }
    if (heavy != -1) hld(heavy);
    for (int v : g[u]){
        if (v != p[u] && v != heavy){
            numChain++;
            hld(v);
        }
    }
}

int lca(int u , int v){
    while (chain[u] != chain[v]){
        if (h[head[chain[u]]] > h[head[chain[v]]]) swap(u , v);
        v = p[head[chain[v]]];
    }
    if (h[u] > h[v]) swap(u , v);
    return u;
}

struct fenwick{
    int t[maxN];

    void reset(){
        for (int i = 1 ; i <= n ; i++) t[i] = 0;
    }

    void update(int x , int y){
        for (; x <= n ; x += x&-x) t[x] += y;
    }

    void update(int l , int r , int x){
        update(l , +x);
        update(r + 1 , -x);
    }

    int get(int x){
        int ans = 0;
        for (; x >= 1 ; x -= x&-x) ans += t[x];
        return ans;
    }
} fen;

ii E[maxN];
int res[maxN];
vector<int> event[2 * maxN] , query[2 * maxN];

void TH1(){
    for (int i = 1 ; i <= n ; i++){
        event[d[p[i]] + maxN].push_back(i);
    }
    for (int i = 1 ; i <= q ; i++){
        query[d[E[i].fi] + maxN].push_back(i);
    }
    for (int i = -n ; i <= +n ; i++){
        for (int id : query[i + maxN]){
            int u = E[id].fi;
            int v = E[id].se;
            int x = fa[id];
            res[id] += fen.get(in[u]) - fen.get(in[p[x]]);
        }
        for (int id : event[i + maxN]){
            fen.update(in[id] , out[id] , +1);
        }
    }
}

void TH2(){
    for (int i = -n ; i <= +n ; i++) event[i + maxN].clear() , query[i + maxN].clear();
    fen.reset();
    for (int i = 1 ; i <= n ; i++){
        event[d[i] + maxN].push_back(i);
    }
    for (int i = 1 ; i <= q ; i++){
        int u = E[i].fi;
        int v = E[i].se;
        int x = fa[i];
        query[d[p[x]] - (d[u] - d[x]) + maxN].push_back(i);
    }
    for (int i = +n ; i >= -n ; i--){
        for (int id : query[i + maxN]){
            int u = E[id].fi;
            int v = E[id].se;
            int x = fa[id];
            res[id] += fen.get(in[v]) - fen.get(in[p[x]]);
            if (d[u] - d[p[x]] > 0) res[id]--;
        }
        for (int id : event[i + maxN]){
            fen.update(in[id] , out[id] , +1);
        }
    }
}

void solve(){
    cin >> n >> q >> s;
    s = '#' + s;
    for (int i = 1 ; i <= n ; i++) a[i] = (s[i] == '+') ? +1 : -1;
    for (int i = 1 ; i < n ; i++){
        int u , v;
        cin >> u >> v;
        g[u].push_back(v);
        g[v].push_back(u);
    }
    d[0] = 0;
    dfs(1);
    hld(1);
    for (int i = 1 ; i <= q ; i++){
        int u , v;
        cin >> u >> v;
        E[i] = {u , v};
        fa[i] = lca(u , v);
    }
    TH1();
    TH2();
    for (int i = 1 ; i <= q ; i++) cout << res[i] << "\n";
}

#define name "A"

int main(){
    ios_base::sync_with_stdio(0); cin.tie(0); cout.tie(0);
    // freopen(name".inp" , "r" , stdin);
    // freopen(name".out" , "w" , stdout);
    int t = 1; //cin >> t;
    while (t--) solve();
    return 0;
}