42 lines
752 B
C++
42 lines
752 B
C++
#include<iostream>
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#include<iomanip>
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int point(double );
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using namespace std;
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int main()
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{
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int n;
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while(cin>>n)
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{
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double sum=0,s,p,c=0;
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while(n--)
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{
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cin>>s>>p;
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if(p==-1)
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continue;
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else
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{
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sum+=s;
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c+=s*point(p);
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}
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}
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if(c==0)
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cout<<"-1\n";
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else
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cout<<setiosflags(ios::fixed)<<setprecision(2)<<c/sum<<endl;
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}
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return 0;
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}
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int point(double g)
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{
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if(g>=90)
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return 4;
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else if(g>=80)
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return 3;
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else if(g>=70)
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return 2;
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else if(g>=60)
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return 1;
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else
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return 0;
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}
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