求a^b的最后一位，a有1000位，b是long long。

#include
     
      #include
      
       long long y;char x[1005];int n,i,s;int a[10];int l;int find(int s,long long r){    memset(a,0,sizeof(a));    a[0]=1;    a[1]=s;a[2]=s*s%10;    i=2;    while(a[1]!=a[i])a[++i]=a[i-1]*s%10;    if (r==0)return 1;    return a[(r-1)%(i-1)+1];}int main(){    scanf("%d",&n);    while(n--){        scanf("%s%lld",&x,&y);        l=strlen(x);        printf("%d\n",find(x[l-1]-48,y));    }}