What is fast input output?

Answer 1

For fast I / O, you can use the C functions scanf / prinf:
string str;
int a;
scanf("%s%d", &str, &a);
printf("%s%d", &str, &a);
OR just add ios_base::sync_with_stdio(0); to the begining main function:
ios_base::sync_with_stdio(0);
string str;
int a;
cin>>str>>a;
cout<<str<<a;