View Compilation Error

0_0_20077878_31042.c: In function 'main':
0_0_20077878_31042.c:14:13: error: 'cout' undeclared (first use in this function)
             cout<<res<<endl;
             ^
0_0_20077878_31042.c:14:13: note: each undeclared identifier is reported only once for each function it appears in
0_0_20077878_31042.c:14:24: error: 'endl' undeclared (first use in this function)
             cout<<res<<endl;
                        ^