include<stdio.h>

int main()
{int n,m,i,a[20],tag,flag=1;
while(scanf("%d",&n)!=EOF)
{for(i=0;i<n;i++)
{scanf("%d",&a[i]);}
scanf("%d",&m);
tag=0;
for(i=0;i<n;i++)
{if(m==a[i])
{tag++;
break;}}
if(tag==1)
{printf("%d",i);}
else
{printf("No");}
printf("\n");
}}