View Compilation Error

0_0_37604531_26902.cpp: In function 'int main()':
0_0_37604531_26902.cpp:71:16: error: missing template arguments before 'a'
         vector a(n + 1, vector<long long>(n + 1));
                ^
0_0_37604531_26902.cpp:74:24: error: 'a' was not declared in this scope
                 cin >> a[i][j];
                        ^
0_0_37604531_26902.cpp:75:53: error: 'a' was not declared in this scope
         cout << "Case #" << cn << ": " << hungarian(a) << "\n";
                                                     ^