View Compilation Error

0_0_16023587_19140.cpp:2:20: error: 'sum' does not name a type
 int n,a,b,i,j,sum; sum=0;
                    ^
0_0_16023587_19140.cpp:3:1: error: expected unqualified-id before 'while'
 while(scanf("%d\n",&n)!=-1) {
 ^