15 lines
188 B
C++
15 lines
188 B
C++
#include<cstdio>
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using namespace std;
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int f(int n,int k)
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{
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if(n>1) return (k-1)*f(n-1,2)+f(n-1,3);
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return k;
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}
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int main()
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{
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int n;
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scanf("%d",&n);
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printf("%d\n",f(n,3));
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return 0;
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}
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