Problem:
Score : 1000 points

Problem Statement

You are given a sequence a = \{a_1, ..., a_N\} with all zeros, and a sequence b = \{b_1, ..., b_N\} consisting of 0 and 1. The length of both is N.

You can perform Q kinds of operations. The i-th operation is as follows:

Replace each of a_{l_i}, a_{l_i + 1}, ..., a_{r_i} with 1.

Minimize the hamming distance between a and b, that is, the number of i such that a_i \neq b_i, by performing some of the Q operations.

Constraints

1 \leq N \leq 200,000

b consists of 0 and 1.

1 \leq Q \leq 200,000

1 \leq l_i \leq r_i \leq N

If i \neq j, either l_i \neq l_j or r_i \neq r_j.

Input

Input is given from Standard Input in the following format:

N
b_1 b_2 ... b_N
Q
l_1 r_1
l_2 r_2
:
l_Q r_Q

Output

Print the minimum possible hamming distance.

Sample Input 1

3
1 0 1
1
1 3

Sample Output 1

1

If you choose to perform the operation, a will become \{1, 1, 1\}, for a hamming distance of 1.

Sample Input 2

3
1 0 1
2
1 1
3 3

Sample Output 2

0

If both operations are performed, a will become \{1, 0, 1\}, for a hamming distance of 0.

Sample Input 3

3
1 0 1
2
1 1
2 3

Sample Output 3

1

Sample Input 4

5
0 1 0 1 0
1
1 5

Sample Output 4

2

It may be optimal to perform no operation.

Sample Input 5

9
0 1 0 1 1 1 0 1 0
3
1 4
5 8
6 7

Sample Output 5

3

Sample Input 6

15
1 1 0 0 0 0 0 0 1 0 1 1 1 0 0
9
4 10
13 14
1 7
4 14
9 11
2 6
7 8
3 12
7 13

Sample Output 6

5

Sample Input 7

10
0 0 0 1 0 0 1 1 1 0
7
1 4
2 5
1 3
6 7
9 9
1 5
7 9

Sample Output 7

1

Solution in C++14 (GCC 5.4.1) (judge verdict: Accepted)

#include<bits/stdc++.h>
using namespace std;
const int maxn=2e5+10,oo=0x3f3f3f3f;

int b[maxn],pre[maxn],n,m,ans;
namespace Seg{
	int a[maxn<<2];
	void clear(){
		memset(a,0x3f,sizeof a);
	}
	#define rt 1,1,n
	#define mid (l+r>>1)
	#define ls u<<1
	#define rs ls|1
	#define lc ls,l,mid
	#define rc rs,mid+1,r
	void update(int u,int l,int r,int ql,int qr,int v){
		if(ql<=l&&r<=qr){
			a[u]=min(a[u],v);
			return;
		}
		//cerr<<u<<" "<<l<<" "<<r<<" "<<ql<<" "<<qr<<endl;
		//system("pause");
		if(ql<=mid)update(lc,ql,qr,v);
		if(qr>mid)update(rc,ql,qr,v);
	}
	int query(int u,int l,int r,int k) {
		if(l==r)return a[u];
		return min(a[u],k<=mid?query(lc,k):query(rc,k));
	}
}
struct data{
	int l,r;
	data(){};
	friend bool operator < (data a,data b){
		if(a.r!=b.r)return a.r<b.r;
		return a.l<b.l;
	}
}p[maxn];
void solve(){
	Seg::clear();
	cin>>n; 
	for(int i=1;i<=n;++i){
		cin>>b[i];
		//scanf("%d",b+i);
		b[i]=b[i]+b[i-1];
	}
	ans=b[n];
	scanf("%d",&m);
	for(int i=1;i<=m;++i){
		cin>>p[i].l>>p[i].r;
		//scanf("%d%d",&p[i].l,&p[i].r);
		//cerr<<p[i].l<<" "<<p[i].r<<endl;
	}
	sort(p+1,p+m+1);
	for(int i=1,l,r,cur=1,w;i<=m;++i){
		l=p[i].l,r=p[i].r;
		for(;cur<r;++cur)pre[cur+1]=pre[cur];
		w=(r-l+1)-(b[r]-b[l-1])+b[l-1]+pre[l-1];
		w=min(w,r-b[r]+Seg::query(1,1,n,l));
		pre[r]=min(pre[r],w-b[r]);
		//cerr<<l<<" "<<r<<endl;
		Seg::update(rt,l,r,w+b[r]-r);
	//cerr<<"wea"<<endl;
		ans=min(ans,w+b[n]-b[r]);
	}
	cout<<ans<<endl;
	//printf("%d\n",ans);
}
int main(){
	solve();
	return 0;
}