def main():
    import sys
    input = sys.stdin.read().split()
    n = int(input[0])
    us = input[1:n+1]
    
    used = set()
    result = []
    
    for u in us:
        # Try split1: S is first character, T is the next two
        s1 = u[0]
        t1 = u[1:3]
        if s1 not in used and t1 not in used:
            result.append((s1, t1))
            used.add(s1)
            used.add(t1)
            continue
        
        # Try split2: S is first two, T is last character
        s2 = u[:2]
        t2 = u[2]
        if s2 not in used and t2 not in used:
            result.append((s2, t2))
            used.add(s2)
            used.add(t2)
            continue
        
        # Neither split works
        print("Impossible")
        return
    
    # Output the result
    for pair in result:
        print(f"{pair[0]} {pair[1]}")

if __name__ == "__main__":
    main()