View Compilation Error

0_0_37593507_21755.cpp:7:1: error: expected initializer before 'const'
 const ll mod = 1e9+7;
 ^
0_0_37593507_21755.cpp: In function 'int main()':
0_0_37593507_21755.cpp:15:9: error: 'll' was not declared in this scope
         ll n,k;
         ^
0_0_37593507_21755.cpp:16:14: error: 'n' was not declared in this scope
         cin>>n>>k;
              ^
0_0_37593507_21755.cpp:16:17: error: 'k' was not declared in this scope
         cin>>n>>k;
                 ^