View Compilation Error

0_0_19496380_9788.cpp: In function 'int main()':
0_0_19496380_9788.cpp:39:13: error: 'i' was not declared in this scope
     mark[a]=i;
             ^
0_0_19496380_9788.cpp:65:35: error: 'i' was not declared in this scope
     while(++l<=r && mark[s[l]] != i);//l每次都到下一个输入过的点
                                   ^