View Compilation Error

0_0_33963061_21742.cpp: In function 'int main()':
0_0_33963061_21742.cpp:50:61: error: request for member 'a' in 'k', which is of non-class type 'int'
       dp[j-skill[k].b] = max(dp[j-skill[k].b],dp[j]-skill[k.a]+t);
                                                             ^