N=int(input())
a=[[i for i in input().split()] for i in range(N)]
R=[0]
i=1
while i <N:
    if a[0][i]=="nyanpass":
        R.append(i)
    i+=1
i=1
while i<N and len(R)>0:
    j=0
    while j<len(R):
        if a[i][R[j]]!="nyanpass" and i!=R[j]:
            R.pop(j)
            j-=1
        j+=1
    i+=1
if len(R)!=1:
    print(-1)
else:
    print(R[0]+1)