View Compilation Error

0_0_38039695_1124.cpp: In function 'int dfs(int, int)':
0_0_38039695_1124.cpp:21:16: error: 'mod' was not declared in this scope
         ans %= mod;
                ^
0_0_38039695_1124.cpp:25:16: error: 'mod' was not declared in this scope
         ans %= mod;
                ^
0_0_38039695_1124.cpp: In function 'int main()':
0_0_38039695_1124.cpp:48:15: error: 'solve' was not declared in this scope
         solve();
               ^