View Compilation Error

0_0_21297108_25308.cpp: In function 'int main()':
0_0_21297108_25308.cpp:6:23: error: 'a' was not declared in this scope
  while( scanf("%d%d",&a,&b) != EOF )
                       ^
0_0_21297108_25308.cpp:6:26: error: 'b' was not declared in this scope
  while( scanf("%d%d",&a,&b) != EOF )
                          ^