int?main(void){
int?n,i,s,t;
printf("Input?n(int?1<n<11)...\nn=");
if(scanf("%d",&n)!=1?||?n<2?||?n>10){
printf("Input?error,?exit...\n");
return?0;
}
for(t=2,s=i=1;i<=n;s+=t,t*=2,i++);
printf("The?result?is?%d\n",s);