this sample code works

#include <stdio.h>
int main(){
long long a,b;
scanf("%lli%lli",&a,&b);
printf("%li",(long)(a+b));
}

and this do not

#include <stdio.h>
int main(){
long long a,b;
scanf("%lli%lli",&a,&b);
printf("%lli",(a+b));
}

same with iostream output
why?