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  1. #include <bits/stdc++.h>
  2. using namespace std;
  3. const int MOD=1e9+7;
  4. int main(){
  5.     int n; cin>>n;
  6.     long long dp[n+1];
  7.     dp[0]=1; dp[1]=1; dp[2]=2;
  8.     for (int i = 3; i <= n; ++i) dp[i]=(dp[i-1]+dp[i-2]+dp[i-3])%MOD;
  9.     cout<<dp[n];
  10.     return 0;
  11. }
Success #stdin #stdout 0.01s 5320KB
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https://ideone.com/K3TUXA
language:
C++ (gcc 8.3)
created:
1 hour ago
visibility:
public

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