View Compilation Error

0_0_36900650_6064.cpp: In function 'void solve(int)':
0_0_36900650_6064.cpp:130:35: error: converting to 'std::vector<std::tuple<int, int, int> >::value_type {aka std::tuple<int, int, int>}' from initializer list would use explicit constructor 'constexpr std::tuple< <template-parameter-1-1> >::tuple(_UElements&& ...) [with _UElements = {int&, int&, int&}; <template-parameter-2-2> = void; _Elements = {int, int, int}]'
         out[u].push_back({a, b, v});
                                   ^
0_0_36900650_6064.cpp:131:34: error: converting to 'std::vector<std::tuple<int, int, int> >::value_type {aka std::tuple<int, int, int>}' from initializer list would use explicit constructor 'constexpr std::tuple< <template-parameter-1-1> >::tuple(_UElements&& ...) [with _UElements = {int&, int&, int&}; <template-parameter-2-2> = void; _Elements = {int, int, int}]'
         in[v].push_back({a, b, u});
                                  ^