Length of integers in C, and input format specifier

In the C standard the number of bits in an ‘int’ is implementation dependent.

How many bits are there in an ‘int’ in CodeChef?

If I want a 64-bit integer, do I need to use ‘long long’? If so, what is its descriptor in ‘scanf’? For example, should I use ‘lld’ like this? (I don’t know how to display ‘&’ without ‘amp;’ following)

long long i;
scanf("%lld", &i);