View Compilation Error

0_0_28952024_6385.cpp: In function 'int main()':
0_0_28952024_6385.cpp:10:12: error: lvalue required as decrement operand
     while(c--){
            ^
0_0_28952024_6385.cpp:12:25: error: 'strlen' was not declared in this scope
         int len=strlen(a);
                         ^