#include <bits/stdc++.h>
using namespace std;
#define PB push_back
#define ZERO (1e-10)
#define INF int(1e9)
#define CL(A,I) (memset(A,I,sizeof(A)))
#define DEB printf("DEB!\n");
#define D(X) cout<<"  "<<#X": "<<X<<endl;
#define EQ(A,B) (A+ZERO>B&&A-ZERO<B)
typedef long long ll;
typedef pair<ll,ll> pll;
typedef vector<int> vi;
typedef pair<int,int> ii;
typedef vector<ii> vii;
#define IN(n) int n;scanf("%d",&n);
#define FOR(i, m, n) for (int i(m); i < n; i++)
#define F(n) FOR(i,0,n)
#define FF(n) FOR(j,0,n)
#define FT(m, n) FOR(k, m, n)
#define aa first
#define bb second
void ga(int N,int *A){F(N)scanf("%d",A+i);}
#define MX 8
#define MQ int(1e6+666)
#define DST(a) (a?a^2?S:R:INF)
vi q;
char c;
int N,M,S,R,Q,g[MX][MX],a,b,G[MX][MX],B[MQ],Z[MQ][MX],D[MQ],d,e,f;
ll T;
void fw(){
    FT(0,N)F(N)FF(N)G[i][j]=min(G[i][j],G[i][k]+G[k][j]);//FW
}
ll sum(){
    ll S=0;
    F(N)S+=G[0][i]<INF?G[0][i]:0;
    return S;
}
int bt(int*z){
    int H=0;
    F(N)H|=(z[i]<<(i*2));
    return H;
}
void deb(){
    F(N)FF(N)printf("%2d%c",g[i][j],j+1==N?10:32);
    puts("----------");
    F(N)FF(N)printf("%2d%c",G[i][j],j+1==N?10:32);
    D(T)
}
void up(int h){
    D[h]=INF;
    F(N)D[h]=min(D[h],DST(Z[d][i])+G[0][i]);
}
int main(void){
    scanf("%d%d%d%d",&N,&M,&Q,&S),CL(g,-1),R=S;
    F(M)scanf("%d%d %c",&a,&b,&c),Z[a][b]=Z[b][a]=1+83-c,g[a][b]=g[b][a]=c^82?S:R;
    F(N)FF(N)G[i][j]=i^j?~g[i][j]?g[i][j]:INF:0;//init
    fw();
    T=sum();
//    deb();
    F(Q){
        scanf("%d%d",&a,&b),d=N+i;
        FF(N)Z[d][j]=(Z[a][j]-Z[b][j]+666)%3;
        e=bt(Z[d]);
        if(!B[e]++){
            q.PB(e);
            bool u=0;
            F(N)if(Z[d][i])FT(i+1,N){
                f=DST(Z[d][i])+DST(Z[d][k]);
                if(G[i][k]>f)G[i][k]=G[k][i]=f,u=1;
            }
            up(e);
            if(D[e]<INF)T+=ll(D[e]);
            if(u){
                fw();
                T=sum();
                for(auto&h:q){
                    up(h);
                    if(D[h]<INF)T+=ll(D[h])*B[h];
                }
            }
        }else T+=D[e]<INF?D[e]:0;
        printf("%lld\n",T);
    }
    return 0;
}