string = input()
a=0
for i in string:
    if(string[a]=="A"):
        print("T",end="")
    if(string[a]=="G"): 
        print("C",end="")
    if(string[a]=="T"): 
        print("A",end="")
    if(string[a]=="C"): 
        print("G",end="")
    a=a+1