#include <bits/stdc++.h>
#define pr pair<int,int>
#define fr first
#define sd second
using namespace std;
namespace l_mid_r{
const int N=3e5+5,B=545,inf=0x3f3f3f3f;
int n,m,a[N],to[N];
vector<int> lx;
vector<vector<pr>> block;
inline int rd(){
int x=0,f=1;char ch=getchar();
while(ch<'0'||ch>'9'){if(ch=='-') f=-1;ch=getchar();}
while(ch>='0'&&ch<='9'){x=x10+ch-48;ch=getchar();}
return xf;
}
int get(int j, int z1, int z2){
auto& vec = block[j];
int l=-1,r=vec.size(),posl=-1,posr=-1;
while(l+1<r){
int mid=(l+r)>>1;
if(vec[mid].fr >= z1) r=mid;
else l=mid;
}
posl=r;
l=-1,r=vec.size();
while(l+1<r){
int mid=(l+r)>>1;
if(vec[mid].fr<=z2) l=mid;
else r=mid;
}
posr=l;
if(posl > posr) return 0;
int min_x=inf;
for(int k=posl; k<=posr; k++){
if(vec[k].sd < min_x){
min_x = vec[k].second;
}
}
return min_x;
}
void upd(int x, int j){
if(!x||!j) return;
auto& vec = block[j];
int l=-1,r=(int)vec.size();
while(l+1<r){
int mid=(l+r)>>1;
if(vec[mid].fr>=a[x]) r=mid;
else l=mid;
}
a[x]=0;
vec.erase(vec.begin()+r);
}
int main(){
freopen("mins.in","r",stdin);
freopen("mins.out","w",stdout);
n=rd(),m=rd();
lx.resize(B+10, 0);
block.resize(B+10);
lx[1] = 1;
int j=1;
for(int i=1; i<=n; i++){
if(i>j*B) j++,lx[j] = i;
to[i]=j,a[i]=rd();
block[j].emplace_back(a[i], i);
}
for(int i=1; i<=j; i++) sort(block[i].begin(), block[i].end());
while(m--){
int x1=rd(),x2=rd(),z1=rd(),z2=rd();
int cnt=inf,bl=0;
int block_x1 = to[x1];
int block_x2 = to[x2];
int u = block_x1 + 1;
int v = block_x2 - 1;
if(u <= v){
for(int i=u;i<=v;i++){
int min_x=get(i,z1,z2);
if(min_x!=0&&min_x<cnt){
cnt=min_x;
bl=i;
break;
}
}
}
int end_x1=(block_x1+1<=j)?lx[block_x1+1]-1:n;
for(int i=x1;i<=end_x1&&i<=x2;i++){
if(i>cnt) break;
if(a[i]>=z1&&a[i]<=z2&&i<cnt) cnt=i,bl= block_x1;
}
int start_x2 = lx[block_x2];
for(int i=start_x2; i<=x2 && i > end_x1; i++){
if(i>cnt) break;
if(a[i]>=z1&&a[i]<=z2&&i<cnt) cnt = i,bl = block_x2;
}
if(cnt ==inf) printf("0\n");
else{
upd(cnt,bl);
printf("%d\n",cnt);
}
}
fclose(stdin);
fclose(stdout);
return 0;
}
}
signed main(){return l_mid_r::main();}
