error in for loop using long long

i am encountering error in this line of the code for(i = 0; i < length; ++i) { scanf("%d",&arr[i]); } where i is long long type and arr is array of int.problem is it does work for i below 1000 but not for larger i like 10000.Do not know what is the problem .if problem is not with this line of code then tell the reason i might get error