26 lines
471 B
C++
26 lines
471 B
C++
#include <iostream>
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#include <cstdio>
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#include <algorithm>
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using namespace std;
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int main()
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{
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int m,n,q,t,p;
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scanf("%d",&t);
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while(t--)
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{
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scanf("%d%d%d%d",&n,&m ,&p,&q);
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int sum=0;
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double op=q/m;
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if(op<p)
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{
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sum+=(n/m)*q;
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int pl=n%m;
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sum+=min(p*pl,q);
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cout<<sum<<endl;
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}
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else
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cout<<p*n<<endl;
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}
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return 0;
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}
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