`scanf()` gets an input from `stdin`, do some formating based on whatever it has given on `*format`

## usage

    #include <stdio.h>
    int 
    scanf(const char *format, ...);


## example

    int i;
    scanf("%251d", &i);


takes an input form `stdin`, puts the first digit of it on `i`.

## return values

return value of scanf depends on whatever if formating worked or failed in some way.