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  1. #include<iostream>
  2. #include<cstdio>
  3. #include<vector>
  4. #include<cmath>
  5. #include<climits>
  6. using namespace std;
  7.  
  8. int pow(int a, int b){
  9.     int ret=1;
  10.     for (int i=0;i<b;i++)
  11.     ret*=a;
  12.    return ret;   
  13. }
  14.  
  15. int main(){
  16.  
  17. 	long long n;
  18. 	cin>>n;
  19. 	long long x=n;
  20. 	long long count=0;
  21. 	while(x>0){
  22.  
  23. 		count++;
  24. 		x/=10;
  25. 	}
  26. 	long long ans=0;
  27. 	ans=(n-pow(10,count-1)+1)*count;
  28. 	for(long long i=count-2;i>=0;i--){
  29.  
  30. 		ans+=9*pow(10,i)*(i+1);
  31. 	}
  32. 	cout<<ans<<endl;
  33. 	cin.get();
  34. 	cin.get();
  35. 	return 0;
  36. }
Success #stdin #stdout 0s 3144KB
comments (?)
stdin
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1000000000
stdout
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8888888899
https://ideone.com/pbIRwP
language:
C++ (gcc 8.3)
created:
9 years ago
visibility:
public

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