#include <iostream>
using namespace std;
int main(){int a,b,c,d,i,n,k;cin>>n>>k>>a>>b;int e[k],f[n+1],p[k][2];
for(i=0;i<k;i++){cin>>p[i][0]>>p[i][1];e[i]=0;}for(i=1;i<=n;i++)f[i]=0;
if(a==b){cout<<a;return 0;}if(a<b){d=0;for(i=0;i<k;i++){if(p[i][0]==1){
if(p[i][1]==n){cout<<a;return 0;}e[i]=1;d++;f[p[i][1]]=a;}else
if(p[i][1]==1){if(p[i][0]==n){cout<<a;return 0;}e[i]=1;d++;f[p[i][0]]=a;}}
c=0;while(!c&&d<k){for(i=0;i<k;i++){if(!e[i]){e[i]=1;if(f[p[i][0]]!=0&&f[p[i][1]]==0)
{f[p[i][1]]=f[p[i][0]]+a;e[i]=1;d++;}else if(f[p[i][0]]==0&&f[p[i][1]]!=0){
f[p[i][0]]=f[p[i][1]]+a;e[i]=1;d++;}if(f[n]>0){c=1;break;}}}}if(f[n]==0)
cout<<b;else cout<<f[n];}return 0;}