View Compilation Error

0_0_34921086_22744.cpp: In function 'void add(std::pair<int, int>)':
0_0_34921086_22744.cpp:39:27: error: no match for 'operator[]' (operand types are 'std::queue<int>' and 'std::queue<int>::size_type {aka long long unsigned int}')
         int tc = nowCol[i][nowCol[i].size() - 1];
                           ^
0_0_34921086_22744.cpp: In function 'void del(std::pair<int, int>)':
0_0_34921086_22744.cpp:64:27: error: no match for 'operator[]' (operand types are 'std::queue<int>' and 'std::queue<int>::size_type {aka long long unsigned int}')
         int tc = nowCol[i][nowCol[i].size() - 1];
                           ^