import
java.io.*;
import
java.util.*;
class
GFG{
static
int
find(
int
v, ArrayList<Integer> parent)
{
if
(parent.get(v) != v)
{
parent.set(v, find(parent.get(v), parent));
return
parent.get(v);
}
return
v;
}
static
void
unions(
int
a,
int
b,
ArrayList<Integer> parent)
{
int
x = find(a, parent);
int
y = find(b, parent);
if
(x != y)
parent.set(x, parent.get(y));
}
static
boolean
equationsPossible(ArrayList<String> relations)
{
ArrayList<Integer> parent =
new
ArrayList<Integer>();
for
(
int
i =
0
; i <
26
; i++)
parent.add(
0
);
for
(
int
i =
0
; i <
26
; i++)
{
parent.set(i, i);
}
int
n = relations.size();
for
(String str : relations)
{
if
(str.charAt(
1
) ==
'='
)
unions((
int
)str.charAt(
0
) -
97
,
(
int
)str.charAt(
3
) -
97
,
parent);
}
for
(String str : relations)
{
if
(str.charAt(
1
) ==
'!'
)
{
int
x = find((
int
)str.charAt(
0
) -
97
,
parent);
int
y = find((
int
)str.charAt(
3
) -
97
,
parent);
if
(x == y)
return
false
;
}
}
return
true
;
}
public
static
void
main (String[] args)
{
ArrayList<String> relations =
new
ArrayList<String>(
Arrays.asList(
"i==j"
,
"j!=i"
));
if
(equationsPossible(relations))
{
System.out.println(
"Yes"
);
}
else
{
System.out.println(
"No"
);
}
}
}