View Compilation Error

0_0_34448228_5057.cpp:20:1: error: expected initializer before 'int'
 int a(int m,int n)
 ^
0_0_34448228_5057.cpp: In function 'int main()':
0_0_34448228_5057.cpp:33:20: error: 'a' was not declared in this scope
         cout<<a(m,n)<<endl;
                    ^