Store/output a number bigger than unsigned long long can store-CodePudding

With user given number (n) for example n=5, I calculate the sum of 10000,10001,10002....99999. Works up until n=17, then I get a negative number or eventually a zero.

So my question is how do I store a number bigger than unsigned long long lets me

#include <iostream>
#include <iomanip>
#include <cmath>

using namespace std;
int main() 
{
  unsigned long long n, sum;
  cin>>n;
  unsigned long long start=pow(10, n-1);
  unsigned long long finish=pow(10, n)-1;
  sum=((finish-start 1)*(start finish))/2;
  cout<<sum<<endl;
  return 0;
}

CodePudding user response：

In case you don't want bother with installing some big number library like GMP, or you do it for some site like code wars then you have basically two options:

A) create your own data type to hold bigger numbers ( in this case not really recommended, as number may be insanely huge).

B) hold it as a string/char table and write a function to process adding values.