View Compilation Error

0_0_23872822_4839.cpp: In function 'int main()':
0_0_23872822_4839.cpp:25:13: error: 'i' was not declared in this scope
    int a=vl[i].a,b=vl[i].b;
             ^
0_0_23872822_4839.cpp:26:10: error: 'b' was not declared in this scope
    while(b--){
          ^