View Compilation Error

0_0_24392333_14771.cpp: In function 'int main()':
0_0_24392333_14771.cpp:7:5: error: 'i' was not declared in this scope
 for(i=0;i<n;i++)
     ^
0_0_24392333_14771.cpp:8:17: error: 'a' was not declared in this scope
 {scanf("%d %d",&a,&b);
                 ^
0_0_24392333_14771.cpp:8:20: error: 'b' was not declared in this scope
 {scanf("%d %d",&a,&b);
                    ^