View Compilation Error

0_0_17861427_6793.cpp: In function 'void solve(int)':
0_0_17861427_6793.cpp:64:26: error: invalid initialization of reference of type 'State& {aka std::vector<int>&}' from expression of type 'const std::vector<int>'
    int k = get_mn(t.first);
                          ^
0_0_17861427_6793.cpp:25:12: note: in passing argument 1 of 'int get_mn(State&)'
 inline int get_mn(State& state) {
            ^