View Compilation Error

0_0_28011988_127.cpp: In function 'int main()':
0_0_28011988_127.cpp:43:14: error: 'sk' was not declared in this scope
      for(k=x;sk!=0&&[k].grade==s[k-1].grade;k--)
              ^
0_0_28011988_127.cpp: In lambda function:
0_0_28011988_127.cpp:43:24: error: expected '{' before '.' token
      for(k=x;sk!=0&&[k].grade==s[k-1].grade;k--)
                        ^
0_0_28011988_127.cpp: In function 'int main()':
0_0_28011988_127.cpp:43:25: error: 'struct main()::<lambda()>' has no member named 'grade'
      for(k=x;sk!=0&&[k].grade==s[k-1].grade;k--)
                         ^