WA at #13求助

#include <bits/stdc++.h>
#define ll long long
#define for(i,k,j) for(ll i=k;i<=j;i++)
using namespace std;
const int N=2e5+5;
const ll INF=1e18;
ll w[N],v[N];
ll l[N],r[N];
ll s[N],s0[N];
ll n,m,st;
ll bg=INF,ed=-1;
ll ans=INF;
ll check(ll x)
{
	ll res=0;
	for(i,0,N) s[i]=s0[i]=0;
	for(i,1,n)
	{
		if(w[i]>=x) s[i]=s[i-1]+v[i],s0[i]=s0[i-1]+1;
		else s[i]=s[i-1],s0[i]=s0[i-1];
	}
	for(i,1,m)
	{
		res+=(s0[r[i]]-s0[l[i]-1])*(s[r[i]]-s[l[i]-1]);
	}
	return res;
}
int main()
{
	scanf("%lld%lld%lld",&n,&m,&st);
	for(i,1,n)
	{
		scanf("%lld%lld",w+i,v+i);
		bg=min(bg,w[i]);
		ed=max(ed,w[i]);
	}
	for(i,1,m) scanf("%lld%lld",l+i,r+i);
	while(bg<ed)
	{
		ll mid=(bg+ed)>>1;
		ll res=check(mid);
		if(res>=st) bg=mid+1;
		else ed=mid;
		ans=min(ans,abs(res-st));
	}
	printf("%lld\n",ans);
	return 0;
}