#include <bits/stdc++.h>
using namespace std;
using ll=long long;
int main(){
	cin.tie(nullptr);
	ios::sync_with_stdio(false);
	int n,m;
	cin>>n>>m;
	vector<vector<pair<ll,int>>> graph(n);
	for(int i=0;i<m;i++){
		int u,v,c;
		cin>>u>>v>>c;
		u--;v--;
		graph[u].push_back(make_pair(c,v));
		//graph[v].push_back(make_pair(c,v));
	}
	string s;
	cin>>s;
	random_device seed;
	mt19937 rnd(seed());
	ll inf=1e18;
	ll ans=inf;
	for(int _=0;_<50;_++){
		vector<int> a(n);
		for(int i=0;i<n;i++){
			if(s[i]=='K'){
				a[i]=0;
			}else if(s[i]=='P'){
				a[i]=2;
			}else if(s[i]=='C'){
				if(rnd()%2)a[i]=1;
				else a[i]=3;
			}else{
				a[i]=-1;
			}
		}
		vector<vector<ll>> dist(n,vector<ll>(4,inf));
		dist[0][0]=0;
		using P=pair<ll,ll>;
		priority_queue<P,vector<P>,greater<P>> pq;
		pq.push(make_pair(0,0));
		while(!pq.empty()){
			auto[d,vs]=pq.top();
			pq.pop();
			ll v=vs%n,s=vs/n;
			if(dist[v][s]<d)continue;
			if(s==a[v]){
				if(s==3)ans=min(ans,d);
				else{
					if(dist[v][s+1]>d){
						dist[v][s+1]=d;
						pq.push(make_pair(d,n*(s+1)+v));
					}
				}
			}
			for(auto[c,u]:graph[v]){
				if(dist[u][s]<=c+d)continue;
				dist[u][s]=c+d;
				pq.push(make_pair(c+d,s*n+u));
			}
		}
	}
	if(ans==inf)cout<<-1<<endl;
	else cout<<ans<<endl;
}