Main.cc:5:1: error: expected initializer before ‘int’
int i,j;
^~~
Main.cc: In function ‘int main()’:
Main.cc:8:7: error: ‘a’ was not declared in this scope
cin>>a;
^
Main.cc:10:2: error: ‘i’ was not declared in this scope
i=0;
^
Main.cc:11:2: error: ‘j’ was not declared in this scope
j=len-1;
^