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AMR10A.cpp
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AMR10A.cpp
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#include <cstdio>
#include <algorithm>
#include<iostream>
#include<vector>
#include<climits>
#include <complex>
#include <iostream>
#include <valarray>
#include<cstring>
#include<queue>
#include<bitset>
#include<map>
#include<set>
#include<sstream>
#include<ctime>
#include <stack>
#include <iomanip>
#include <cassert>
#include<cmath>
using namespace std;
#define PB push_back
#define i64 long long
#define FOR(i,a,b) for(i=(a);i<(b);++i)
#define FORE(i,a,b) for(i=(a);i<=(b);++i)
#define REP(i,n) FOR(i,0,n)
#define REPE(i,n) FORE(i,0,n)
#define SZ(v) ((v).size())
#define LD long double
#define VI vector<int>
#define VS vector<string>
#define VD vector<double>
#define VLD vector<LD>
#define MSET(x,y) memset((x),(y),sizeof(x))
#define SZOF(x) sizeof((x))
#define VVI vector< VI >
#define PII pair< int,int >
#define VPII vector< PII >
#define MP make_pair
#define PIPII pair<int, PII >
#define PIPIPII pair< int, PIPII >
#define u64 unsigned i64
#define Vi64 vector<i64>
#define Vu64 vector<u64>
#define MAXN 50005
i64 x[MAXN],y[MAXN];
i64 arr[MAXN];
int n,m;
int main()
{
freopen("Text/AMR10A.txt","r",stdin);
int a,b;
i64 tt,ans,ans2;
int i;
scanf("%d %d",&n,&m);
for(i=1;i<=n;++i)
{
scanf("%lld %lld",x+i,y+i);
}
x[n+1]=x[1];
y[n+1]=y[1];
for(i=1;i<=n;++i)
{
arr[i]=arr[i-1]+(x[i]*y[i+1]-x[i+1]*y[i]);
}
tt=abs(arr[n]);
while(m--)
{
scanf("%d %d",&a,&b);
ans=arr[b]-arr[a];
ans+=x[b+1]*y[a+1]-x[a+1]*y[b+1];
ans=abs(ans);
ans2=tt-ans;
ans=min(ans,ans2);
double ti=ans;
printf("%.1f\n",ti/2LL);
}
return 0;
}