20 lines
324 B
C++
20 lines
324 B
C++
#include <cmath>
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#include <cstdio>
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#include <cstring>
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#include <cstdlib>
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#include <iomanip>
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#include <iostream>
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using namespace std;
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int main()
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{
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int n,m,i,j,f[1000];
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cin>>n;
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f[1] = 1;
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f[2] = 2;
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f[3] = 4;
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for (i = 4;i <= n;i++)
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f[i] = f[i - 1] + f[i - 2] + f[i - 3];
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cout<<f[n];
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return 0;
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}
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