29 lines
688 B
C++
29 lines
688 B
C++
#include<cstdio>
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#include<cstring>
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#include<iostream>
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using namespace std;
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#define maxn 100005
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#define ll __int64
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ll x[maxn],y[maxn];
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ll sumx[maxn],sumy[maxn];
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int main(){
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ll i,j,k,T,n,C=1;
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scanf("%I64d",&T);
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while(T--){
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scanf("%I64d",&n);
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memset(sumx,0,sizeof(sumx));
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memset(sumy,0,sizeof(sumy));
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for(i=1;i<=n;i++){
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scanf("%I64d%I64d",&x[i],&y[i]);
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sumx[i]=sumx[i-1]+x[i];
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sumy[i]=sumy[i-1]+y[i];
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}
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ll sum=0;
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for(i=1;i<=n;i++){
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sum+=sumx[i-1]*y[i]+sumy[i-1]*x[i];
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}
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printf("Case %I64d: %I64d\n",C++,sum);
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}
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return 0;
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}
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