#include <iostream>
#include <limits>
 
int main()
{
  using namespace std;
 
  char c;
  int sum = 0;
  while ( cin >> c ) // read first character in line
  {
    if ( c == 'a' ) // end of input
      break;
 
    int n;
    if (cin.unget() >> n) // putback in the stream the last read character and try to read an integer
    {
      sum += n;
      continue;
    }
 
    cout << "Invalid input. Please try again.\n";
    cin.clear(); // failed to read an integer: reset the error flags
    cin.ignore(numeric_limits<streamsize>::max(), '\n'); // eat to the end of new-line
  }
 
  cout << "The total sum is " << sum << ".\n";
}

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MQoyCmludmFsaWQgaW5wdXQKMwphaWdub3JlZA==

1
2
invalid input
3
aignored