#include<bits/stdc++.h>
#define int long long
#define lowbit(x) (x&-x)
using namespace std;
const int N=2e5+5,MX=1e9;
int n,m,a[N],b[N],p[N],v[N],sum,c[N],d[N],sb[N],sd[N],b1[N];
struct BIT
{
	int t[N];
	void add(int x,int v){for(int i=x;i<N;i+=lowbit(i))t[i]+=v;}
	int ask(int x){int res=0;for(int i=x;i>=1;i-=lowbit(i))res+=t[i];return res;}
	int  ask1(int x){return ask(N-1)-ask(x-1);}
	void clr(){memset(t,0,sizeof(t));}
}t1,t2;
struct Tree_of_tree
{
	int rt[N],tot;
	struct STree{int lc,rc,sum;}t[N*60];
	void pushup(int p){t[p].sum=t[t[p].lc].sum+t[t[p].rc].sum;}
	void change(int &p,int l,int r,int x,int v)
	{
		if(!p)p=++tot;
		if(l==r)return t[p].sum+=v,void();
		int mid=l+r>>1;
		if(x<=mid)change(t[p].lc,l,mid,x,v);else change(t[p].rc,mid+1,r,x,v);pushup(p);
	}
	int ask(int p,int l,int r,int al,int ar)
	{
		if(al<=l && r<=ar)return t[p].sum;
		int mid=l+r>>1,res=0;
		if(al<=mid)res+=ask(t[p].lc,l,mid,al,ar);if(mid<ar)res+=ask(t[p].rc,mid+1,r,al,ar);
		return res;
	}
	void add(int x,int y){for(int i=x;i<=sb[0];i+=lowbit(i))change(rt[i],1,sd[0],y,1);}
	int ask(int ax,int ay,int by){if(!ax || ay>by)return 0;int res=0;for(int i=ax;i>=1;i-=lowbit(i))res+=ask(rt[i],1,sd[0],ay,by);return res;}
	int ask1(int ax,int bx,int ay,int by){if(ax>bx || ay>by)return 0;return ask(bx,ay,by)-ask(ax-1,ay,by);}
	void clr(){for(int i=1;i<=tot;i++)t[i].lc=t[i].rc=t[i].sum=0;for(int i=1;i<=sb[0];i++)rt[i]=0;tot=0;}
}t3;
int a1=0,vb[N],vd[N],vc[N];
int ans[N];
void solve(int pos)
{
	int ans1=0;
	for(int i=n;i>=1;i--)ans1+=c[i]*t1.ask(b[i]-1)-t2.ask(b[i]-1),t1.add(b[i],1),t2.add(b[i],c[i]);
	t1.clr(),t2.clr();
	for(int i=1;i<=n;i++)ans1+=c[i]*t1.ask(b[i]-1)-t2.ask(b[i]-1),t1.add(b[i],1),t2.add(b[i],c[i]);
	t1.clr(),t2.clr();
	for(int i=n;i>=1;i--)ans1+=t3.ask(b[i]-1,1,d[i]-1),t3.add(b[i],d[i]);
	t3.clr();
	for(int i=1;i<=n;i++)ans1-=t3.ask(b[i]-1,d[i]+1,sd[0]),t3.add(b[i],d[i]);
	t3.clr();
	a1=ans1,ans[pos]=ans1;
}
vector<int>que[N];
int nss,vis1[N];
void add(int x){vis1[x]++;if(vis1[x]==1)nss++;}
void del(int x){vis1[x]--;if(!vis1[x])nss--;}
signed main()
{
	scanf("%lld %lld",&n,&m);
	for(int i=1;i<=n;i++)scanf("%lld",&a[i]);
	for(int i=1;i<=n;i++)if(i&1)a[i]*=-1;
	for(int i=1;i<=n;i++)b[i]=b[i-1]+a[i];
	for(int i=1;i<=m;i++)
	{
		scanf("%lld %lld",&p[i],&v[i]),p[i]++;
		if(p[i]&1)v[i]*=-1;
	}
	sum=b[n];
	if(sum<0)
	{
		sum*=-1;
		for(int i=1;i<=n;i++)b[i]*=-1;
		for(int i=1;i<=m;i++)v[i]*=-1;
	}
	if(sum<n || n%2==1)
	{
		for(int i=1;i<=m;i++)printf("-1\n");
		return 0;
	}
	for(int i=1;i<=n;i++)b[i]+=sum*MX;
	for(int i=1;i<=n;i++)c[i]=b[i]/sum,d[i]=b[i]%sum;
	for(int i=1;i<=n;i++)sb[++sb[0]]=b[i],sd[++sd[0]]=d[i];
	for(int i=1;i<=m;i++)sb[++sb[0]]=b[p[i]]+v[i],sd[++sd[0]]=(b[p[i]]+v[i])%sum;
	sort(sb+1,sb+sb[0]+1),sb[0]=unique(sb+1,sb+sb[0]+1)-sb-1;
	sort(sd+1,sd+sd[0]+1),sd[0]=unique(sd+1,sd+sd[0]+1)-sd-1;
	for(int i=1;i<=m;i++)vc[i]=(b[p[i]]+v[i])/sum,vd[i]=lower_bound(sd+1,sd+sd[0]+1,(b[p[i]]+v[i])%sum)-sd,vb[i]=lower_bound(sb+1,sb+sb[0]+1,b[p[i]]+v[i])-sb;
	for(int i=1;i<=n;i++)b[i]=lower_bound(sb+1,sb+sb[0]+1,b[i])-sb,d[i]=lower_bound(sd+1,sd+sd[0]+1,d[i])-sd;
	solve(0);
	int cnt=0;
	for(int i=1;i<=n;i++)add(d[i]);
	for(int i=1;i<=m;i++)
	{
		del(d[p[i]]),add(vd[i]);
		if(nss!=n)ans[i]=-1;else ans[i]=ans[0];
		del(vd[i]),add(d[p[i]]);
	}
	for(int i=1;i<=m;i++)if(ans[i]!=-1)que[p[i]].push_back(i);
	for(int i=n;i>=1;i--)
	{
		for(auto j:que[i])
		{
			ans[j]+=t3.ask(vb[j]-1,1,vd[j]-1)-t3.ask(b[i]-1,1,d[i]-1);
			ans[j]-=t3.ask1(vb[j]+1,sb[0],1,vd[j]-1)-t3.ask1(b[i]+1,sb[0],1,d[i]-1);
		}
		t3.add(b[i],d[i]);
	}
	t3.clr();
	for(int i=1;i<=n;i++)
	{
		for(auto j:que[i])
		{
			ans[j]-=t3.ask(vb[j]-1,vd[j]+1,sd[0])-t3.ask(b[i]-1,d[i]+1,sd[0]);
			ans[j]+=t3.ask1(vb[j]+1,sb[0],vd[j]+1,sd[0])-t3.ask1(b[i]+1,sb[0],d[i]+1,sd[0]);
		}
		t3.add(b[i],d[i]);
	}
	t3.clr();
	for(int i=n;i>=1;i--)
	{
		for(auto j:que[i])
		{
			ans[j]+=vc[j]*t1.ask(vb[j]-1)-t2.ask(vb[j]-1);
			ans[j]-=c[i]*t1.ask(b[i]-1)-t2.ask(b[i]-1);
			ans[j]+=-vc[j]*t1.ask1(vb[j]+1)+t2.ask1(vb[j]+1);
			ans[j]-=-c[i]*t1.ask1(b[i]+1)+t2.ask1(b[i]+1);
		}
		t1.add(b[i],1),t2.add(b[i],c[i]);
	}
	t1.clr(),t2.clr();
	for(int i=1;i<=n;i++)
	{
		for(auto j:que[i])
		{
			ans[j]+=vc[j]*t1.ask(vb[j]-1)-t2.ask(vb[j]-1);
			ans[j]-=c[i]*t1.ask(b[i]-1)-t2.ask(b[i]-1);
			ans[j]+=-vc[j]*t1.ask1(vb[j]+1)+t2.ask1(vb[j]+1);
			ans[j]-=-c[i]*t1.ask1(b[i]+1)+t2.ask1(b[i]+1);
		}
		t1.add(b[i],1),t2.add(b[i],c[i]);
	}
	t1.clr(),t2.clr();
	for(int i=1;i<=m;i++)printf("%lld\n",ans[i]);
	return 0;
}