#include<bits/stdc++.h>
#include<atcoder/all>
using namespace std;
using namespace atcoder;
typedef long long int ll;
typedef long double ld;
typedef vector<int> vi;
typedef vector<ll> vl;
typedef vector<vl> vvl;
typedef vector<vvl> vvvl;
typedef vector<vvvl> vvvvl;
typedef vector<bool> vb;
typedef vector<vb> vvb;
typedef vector<vvb> vvvb;
typedef vector<vvvb> vvvvb;
typedef pair<ll,ll> pl;
typedef pair<ll,pl> ppl;
typedef pair<ll,ppl> pppl;
typedef pair<ll,pppl> pppppl;
#define rep(i,a,b) for(int i=(a);i<(b);i++)
#define rrep(i,a,b) for(int i=(b)-1;i>=(a);i--)
#define all(a) begin(a),end(a)
#define sz(a) (int)(a).size()
#define F first
#define S second
#define bs(A,x) binary_search(all(A),x)
#define lb(A,x) (ll)(lower_bound(all(A),x)-A.begin())
#define ub(A,x) (ll)(upper_bound(all(A),x)-A.begin())
#define cou(A,x) (ll)(upper_bound(all(A),x)-lower_bound(all(A),x))
template<typename T>using min_priority_queue=priority_queue<T,vector<T>,greater<T>>;
template<class T>bool chmax(T&a,T b){if(a<b){a=b;return 1;}return 0;}
template<class T>bool chmin(T&a,T b){if(b<a){a=b;return 1;}return 0;}
//*
using mint=modint998244353;
const ll mod=998244353;
//*/
/*
using mint=modint1000000007;
const ll mod=1000000007;
//*/
//using mint=modint;
//*
typedef vector<mint> vm;
typedef vector<vm> vvm;
typedef vector<vvm> vvvm;
typedef vector<vvvm> vvvvm;
ostream&operator<<(ostream&os,mint a){os<<a.val();return os;}
istream&operator>>(istream&is,mint&a){int x;is>>x;a=mint(x);return is;}
//*/
template<typename T1,typename T2>ostream&operator<<(ostream&os,pair<T1,T2>p){os<<p.F<<" "<<p.S;return os;}
template<typename T1,typename T2>istream&operator>>(istream&is,pair<T1,T2>&p){is>>p.F>>p.S;return is;}
template<typename T>ostream&operator<<(ostream&os,vector<T>v){rep(i,0,sz(v))os<<v[i]<<(i+1!=sz(v)?" ":"");return os;}
template<typename T>istream&operator>>(istream&is,vector<T>&v){for(T&in:v)is>>in;return is;}
int main(){
  cin.tie(0)->sync_with_stdio(0);
  cin.exceptions(cin.failbit);
  ll N,M;cin>>N>>M;
  vector<vector<pl>>E(N);
  rep(i,0,M){
    ll u,v,w;cin>>u>>v>>w;u--;v--;
    E[u].emplace_back(v,w);
  }
  string S;cin>>S;
  
  vl D(N,1e18);
  D[0]=0;
  min_priority_queue<pl>Q;
  Q.emplace(0,0);
  while(sz(Q)){
    auto[d,v]=Q.top();Q.pop();
    if(D[v]!=d)continue;
    for(auto[u,w]:E[v])if(chmin(D[u],D[v]+w))Q.emplace(D[u],u);
  }
  rep(i,0,N){
    if(S[i]!='K')D[i]=1e18;
    else Q.emplace(D[i],i);
  }
  while(sz(Q)){
    auto[d,v]=Q.top();Q.pop();
    if(D[v]!=d)continue;
    for(auto[u,w]:E[v])if(chmin(D[u],D[v]+w))Q.emplace(D[u],u);
  }
  vector<pair<pl,pl>>DD(N,make_pair(pl(1e18,1e18),pl(1e18,1e18)));
  min_priority_queue<pair<pair<pl,pl>,ll>>QQ;
  rep(i,0,N)if(S[i]=='C')DD[i].F=pl(D[i],i),QQ.emplace(DD[i],i);
  while(sz(QQ)){
    auto[dd,v]=QQ.top();QQ.pop();
    if(dd!=DD[v])continue;
    auto[p,q]=dd;
    for(auto[u,w]:E[v]){
      vector<pl>F;
      if(p.S<1e17)F.emplace_back(p.F+w,p.S);
      if(q.S<1e17)F.emplace_back(q.F+w,q.S);
      if(DD[u].F.S<1e17)F.emplace_back(DD[u].F);
      if(DD[u].S.S<1e17)F.emplace_back(DD[u].S);
      sort(all(F));
      {
        set<ll>st;
        vector<pl>_F;
        for(auto[p,q]:F){
          if(!st.count(q))_F.emplace_back(p,q);
          st.emplace(q);
        }
        F=_F;
      }
      if(sz(F)==1)F.emplace_back(1e18,1e18);
      if(DD[u]!=make_pair(F[0],F[1])){
        DD[u]=make_pair(F[0],F[1]);
        QQ.emplace(DD[u],u);
      }
    }
  }
  rep(i,0,N){
    if(S[i]!='P')DD[i]=make_pair(pl(1e18,1e18),pl(1e18,1e18));
    else if(DD[i].F.S<1e17)QQ.emplace(DD[i],i);
  }
  while(sz(QQ)){
    auto[dd,v]=QQ.top();QQ.pop();
    if(dd!=DD[v])continue;
    auto[p,q]=dd;
    for(auto[u,w]:E[v]){
      vector<pl>F;
      if(p.S<1e17)F.emplace_back(p.F+w,p.S);
      if(q.S<1e17)F.emplace_back(q.F+w,q.S);
      if(DD[u].F.S<1e17)F.emplace_back(DD[u].F);
      if(DD[u].S.S<1e17)F.emplace_back(DD[u].S);
      sort(all(F));
      {
        set<ll>st;
        vector<pl>_F;
        for(auto[p,q]:F){
          if(!st.count(q))_F.emplace_back(p,q);
          st.emplace(q);
        }
        F=_F;
      }
      if(sz(F)==1)F.emplace_back(1e18,1e18);
      if(DD[u]!=make_pair(F[0],F[1])){
        DD[u]=make_pair(F[0],F[1]);
        QQ.emplace(DD[u],u);
      }
    }
  }
  ll ans=1e18;
  rep(i,0,N)if(S[i]=='C'){
    if(DD[i].F.S!=i)chmin(ans,DD[i].F.F);
    if(DD[i].S.S!=i)chmin(ans,DD[i].S.F);
  }
  if(ans>1e17)ans=-1;
  cout<<ans<<endl;
  return 0;
}