View Compilation Error

0_0_23048164_9885.cpp: In function 'int main()':
0_0_23048164_9885.cpp:20:17: error: 'i' was not declared in this scope
             for(i=0;i<=len-1;i++)
                 ^
0_0_23048164_9885.cpp:20:24: error: 'len' was not declared in this scope
             for(i=0;i<=len-1;i++)
                        ^
0_0_23048164_9885.cpp:22:21: error: 'len' was not declared in this scope
             if(sum==len)cout<<"yes"<<endl;
                     ^