View Compilation Error

0_0_18614154_1581.cpp: In function 'int main()':
0_0_18614154_1581.cpp:25:6: error: 'i' was not declared in this scope
   if(i!=s.size()-1)
      ^
0_0_18614154_1581.cpp:28:16: error: 'i' was not declared in this scope
   s=s.substr(0,i+1);
                ^