View Compilation Error

0_0_13233991_9160.cpp: In function 'int main(int, char**)':
0_0_13233991_9160.cpp:12:9: error: 'gtes' was not declared in this scope
   gtes(a);
         ^
0_0_13233991_9160.cpp:14:22: error: 'strlen' was not declared in this scope
   for(i=0;i<=strlen(a);i++){
                      ^