#include <bits/stdc++.h>
using namespace std;

vector<long long> dijkstra(vector<vector<pair<int,long long>>> &Graph,int start){
int N = Graph.size();
//O((V+E)logV) 一般最短経路魔法.
long long inf = 3e18;
    vector<bool> used(N);
    vector<long long> ret(N,inf);
    priority_queue<pair<long long,int>,vector<pair<long long,int>>,greater<pair<long long,int>>> Q;
    ret.at(start) = 0; Q.push({0,start});
    while(Q.size()){
        auto[nowd,pos] = Q.top(); Q.pop();
        if(used.at(pos)) continue;
        used.at(pos) = true;
        for(auto [to,w] : Graph.at(pos)){
            if(ret.at(to) > nowd+w){
                ret.at(to) = nowd+w;
                Q.push({ret.at(to),to});
            }
        }
    }
    return ret;
}
vector<long long> dijkstra2(vector<vector<pair<int,long long>>> &Graph,int start){
    int N = Graph.size();
    //O(V^2) 密グラフ専用.
    long long inf = 3e18;
    vector<bool> used(N);
    vector<long long> ret(N,inf);
    ret.at(start) = 0;
    while(true){
        long long nowd = inf,pos = -1;
        for(int i=0; i<N; i++){
            if(used.at(i)) continue;
            if(nowd > ret.at(i)) nowd = ret.at(i),pos = i;
        }
        if(pos == -1) break;
        used.at(pos) = true;
 
        for(auto [to,w] : Graph.at(pos)){if(ret.at(to) > nowd+w) ret.at(to) = nowd+w;}
    }
    return ret;
}

int main(){
    ios_base::sync_with_stdio(false);
    cin.tie(nullptr);
    
    int N,M; cin >> N >> M;
    vector<tuple<int,int,int>> edge(M);
    for(auto &[u,v,c] : edge) cin >> u >> v >> c,u--,v--;
    string s; cin >> s;
    long long answer = 1e18;
    vector<vector<pair<int,long long>>> Graph(5*N);
    for(auto [u,v,c] : edge) for(int i=0; i<5; i++) Graph.at(u*5+i).push_back({v*5+i,c});
    for(int i=0; i<N; i++){
        if(s.at(i) == 'K') Graph.at(i*5).push_back({i*5+1,0});
        if(s.at(i) == 'P') Graph.at(i*5+2).push_back({i*5+3,0});
    }
    for(int t=0; t<17; t++){
        vector<bool> one(N);
        for(int i=0; i<N; i++) one.at(i) = (i>>t)&1;
        for(int i=0; i<N; i++) if(s.at(i) == 'C') Graph.at(i*5+(one.at(i)?3:1)).push_back({i*5+(one.at(i)?4:2),0});    
        answer = min(answer,dijkstra(Graph,0).back());
        for(int i=0; i<N; i++) if(s.at(i) == 'C') Graph.at(i*5+(one.at(i)?3:1)).pop_back();

        for(int i=0; i<N; i++) if(s.at(i) == 'C') Graph.at(i*5+(one.at(i)?1:3)).push_back({i*5+(one.at(i)?2:4),0});    
        answer = min(answer,dijkstra(Graph,0).back());
        for(int i=0; i<N; i++) if(s.at(i) == 'C') Graph.at(i*5+(one.at(i)?1:3)).pop_back();
    }
    if(answer > 1e17) answer = -1; 
    cout << answer << endl;
}