import sequtils,strutils
var
    N = stdin.readline.parseInt
    S = newSeqWith(N, newSeq[string](N))
    ans,cnt : int

for n in 0..<N:
    S[n] = stdin.readline.split

for j in 0..<N:
    var f = false
    for i in 0..<N:
        if i != j and S[i][j] != "nyanpass":
            f = false
    if f:
        cnt += 1
        ans = j

if cnt == 1:
    echo ans + 1
else:
    echo -1