/in/foo.cc: In function 'int main()':
/in/foo.cc:7:14: error: conflicting declaration 'char sum [100]'
  char sum[100];
              ^
/in/foo.cc:5:12: note: previous declaration as 'int sum'
  int k1,k2,sum=0;
            ^~~
/in/foo.cc:8:2: error: 's' was not declared in this scope
  s[0]=1;
  ^
/in/foo.cc:10:21: error: 'k' was not declared in this scope
     for (int i=2;i<=k;i++)
                     ^
/in/foo.cc:14:12: error: 'j' was not declared in this scope
  for(int i=j-1;i<k;i++)
            ^
/in/foo.cc:14:18: error: 'k' was not declared in this scope
  for(int i=j-1;i<k;i++)
                  ^