Driver code
int main ( ) { string s = "45" ; cout << primeDigits ( s ) << endl ; s = "1000" ; cout << primeDigits ( s ) << endl ; s = "7721" ; cout << primeDigits ( s ) << endl ; s = "7221" ; cout << primeDigits ( s ) << endl ; s = "74545678912345689748593275897894708927680" ; cout << primeDigits ( s ) << endl ; return 0 ; }