#include <bits/stdc++.h>
using namespace std;
typedef signed long long ll;

#define _P(...) (void)printf(__VA_ARGS__)
#define FOR(x,to) for(x=0;x<(to);x++)
#define FORR(x,arr) for(auto& x:arr)
#define FORR2(x,y,arr) for(auto& [x,y]:arr)
#define ALL(a) (a.begin()),(a.end())
#define ZERO(a) memset(a,0,sizeof(a))
#define MINUS(a) memset(a,0xff,sizeof(a))
template<class T> bool chmax(T &a, const T &b) { if(a<b){a=b;return 1;}return 0;}
template<class T> bool chmin(T &a, const T &b) { if(a>b){a=b;return 1;}return 0;}
//-------------------------------------------------------

int N,M;
vector<pair<int,int>> E[202020];
string S;
pair<ll,int> dp[202020][5][2];



void solve() {
	int i,j,k,l,r,x,y; string s;
	
	cin>>N>>M;
	FOR(i,N) FOR(j,5) dp[i][j][0]=dp[i][j][1]={1LL<<60,-1};
	priority_queue<pair<ll,int>> Q;
	dp[0][0][0]={0,-1};
	Q.push({0,0});
	FOR(i,M) {
		cin>>x>>y>>k;
		E[x-1].push_back({y-1,k});
	}
	cin>>S;
	ll ret=1LL<<60;
	while(Q.size()) {
		ll co=-Q.top().first;
		int cur=Q.top().second/10;
		int id=Q.top().second/2%5;
		int order=Q.top().second%2;
		Q.pop();
		if(co!=dp[cur][id][order].first) continue;
		//cout<<cur<<" "<<id<<" "<<order<<" "<<co<<" "<<dp[cur][id][order].second<<endl;
		if(id==4) {
			cout<<co<<endl;
			return;
		}
		int nc=dp[cur][id][order].second;
		if(S[cur]=='K'&&id==0&&chmin(dp[cur][1][0].first,co)) Q.push({-co,cur*10+1*2+0});
		if(S[cur]=='C'&&id==1) {
			if(co<dp[cur][2][0].first&&dp[cur][2][0].second==cur) {
				dp[cur][2][0].first=co;
				Q.push({-co,cur*10+2*2+0});
			}
			else if(co<dp[cur][2][0].first&&dp[cur][2][0].second!=cur) {
				dp[cur][2][1]=dp[cur][2][0];
				dp[cur][2][0]={co,cur};
				Q.push({-co,cur*10+2*2+0});
				Q.push({-dp[cur][2][1].first,cur*10+2*2+1});
			}
			else if(co<dp[cur][2][1].first&&dp[cur][2][0].second!=cur) {
				dp[cur][2][1]={co,cur};
				Q.push({-dp[cur][2][1].first,cur*10+2*2+1});
			}
		}
		if(S[cur]=='P'&&id==2) {
			if(co<dp[cur][3][0].first&&dp[cur][3][0].second==nc) {
				dp[cur][3][0].first=co;
				Q.push({-co,cur*10+3*2+0});
			}
			else if(co<dp[cur][3][0].first&&dp[cur][3][0].second!=nc) {
				dp[cur][3][1]=dp[cur][3][0];
				dp[cur][3][0]={co,nc};
				Q.push({-co,cur*10+3*2+0});
				Q.push({-dp[cur][3][1].first,cur*10+3*2+1});
			}
			else if(co<dp[cur][3][1].first&&nc!=dp[cur][3][0].second) {
				dp[cur][2][1]={co,nc};
				Q.push({-dp[cur][3][1].first,cur*10+3*2+1});
			}
		}
		if(S[cur]=='C'&&id==3) {
			if(nc!=cur) ret=min(ret,co);
		}
		if(id<=1) {
			FORR2(e,c,E[cur]) if(chmin(dp[e][id][0].first,co+c)) Q.push({-dp[e][id][0].first,e*10+id*2});
		}
		else {
			FORR2(e,c,E[cur]) {
				if(co+c<dp[e][id][0].first) {
					if(nc==dp[e][id][0].second) {
						dp[e][id][0].first=co+c;
						Q.push({-dp[e][id][0].first,e*10+id*2+0});
					}
					else {
						dp[e][id][1]=dp[e][id][0];
						dp[e][id][0]={co+c,nc};
						Q.push({-dp[e][id][0].first,e*10+id*2+0});
						Q.push({-dp[e][id][1].first,e*10+id*2+1});
					}
				}
				else if(co+c<dp[e][id][1].first&&nc!=dp[e][id][0].second) {
					dp[e][id][1]={co+c,nc};
					Q.push({-dp[e][id][1].first,e*10+id*2+1});
				}
			}
		}
	}
	if(ret>=1LL<<60) ret=-1;
	cout<<ret<<endl;
}


int main(int argc,char** argv){
	string s;int i;
	if(argc==1) ios::sync_with_stdio(false), cin.tie(0);
	FOR(i,argc-1) s+=argv[i+1],s+='\n'; FOR(i,s.size()) ungetc(s[s.size()-1-i],stdin);
	cout.tie(0); solve(); return 0;
}