View Compilation Error

0_0_18329433_24025.c: In function 'main':
0_0_18329433_24025.c:6:21: error: 'A' undeclared (first use in this function)
 while(scanf("%d%d",&A,&B)!=EOF){
                     ^
0_0_18329433_24025.c:6:21: note: each undeclared identifier is reported only once for each function it appears in
0_0_18329433_24025.c:6:24: error: 'B' undeclared (first use in this function)
 while(scanf("%d%d",&A,&B)!=EOF){
                        ^