#pragma GCC target("avx2")
#pragma GCC optimization("O3")
#pragma GCC optimization("unroll-loops")
#include <bits/stdc++.h>
#define rc(x) return cout<<x<<endl,0
#define pb push_back
#define mkp make_pair
#define in insert
#define er erase
#define fd find
#define fr first
#define sc second
typedef long long ll;
typedef long double ld;
const ll INF=0x3f3f3f3f3f3f3f3f;
const ll llinf=(1LL<<62);
const int inf=(1<<30);
const int nmax=5e4+50;
const int mod=1e9+7;
using namespace std;
int k,n,m,x,y,t,f[nmax],z,i,j,q,g[nmax],u[nmax],c[nmax];
vector<pair<int,int> >a[nmax];
int main()
{
//freopen("sol.in","r",stdin);
//freopen("sol.out","w",stdout);
//mt19937 rng(chrono::steady_clock::now().time_since_epoch().count());
ios_base::sync_with_stdio(false);cin.tie(0);cerr.tie(0);cout.tie(0);
cin>>k>>n>>m>>q;
while(m--)
{
cin>>x>>y>>t;
a[x].pb(mkp(y,t));
}
for(i=0;i<n;i++)g[i]=u[i]=c[i]=inf;
g[0]=0;
u[0]=0;
c[0]=0;
for(i=0;i<n;i++)
{
if(g[i]==inf)continue;
for(j=0;j<(int)a[i].size();j++)
{
z=a[i][j].fr,t=a[i][j].sc;
g[z]=min(g[z],g[i]+t);
}
}
for(i=0;i<n;i++)
{
if(u[i]==inf)u[i]=i,c[i]=0;
for(j=0;j<(int)a[i].size();j++)
{
z=a[i][j].fr,t=a[i][j].sc;
u[z]=min(u[z],u[i]);
c[z]=min(c[z],c[i]+t);
}
}
while(q--)
{
cin>>x>>y;
if(y/k<=x/k)cout<<-1<<'\n';
else if(!x)
{
if(g[y]==inf)cout<<-1<<'\n';
else cout<<g[y]<<'\n';
}
else if(k==1)
{
if(u[y]>x)cout<<-1<<'\n';
else cout<<c[y]-c[x]<<'\n';
}
else
{
for(i=x;i<=y;i++)f[i]=inf;
f[x]=0;
for(i=x;i<=y;i++)
{
if(f[i]==inf)continue;
for(j=0;j<(int)a[i].size();j++)
{
z=a[i][j].fr,t=a[i][j].sc;
f[z]=min(f[z],f[i]+t);
}
}
if(f[y]==inf)cout<<-1<<'\n';
else cout<<f[y]<<'\n';
}
}
return 0;
}
