foo.cpp: In function 'void floyd()':
foo.cpp:8:20: error: 'n' was not declared in this scope
   { for(int k=1;k<=n;k++)
                    ^
foo.cpp: In function 'int main()':
foo.cpp:17:18: error: 'n' was not declared in this scope
   for(int i=1;i<=n;i++)
                  ^
foo.cpp:18:22: error: 'x' was not declared in this scope
    while(scanf("%d",&x)!=0)
                      ^
foo.cpp:22:18: error: 'n' was not declared in this scope
   for(int i=1;i<=n;i++)
                  ^