codeforces630C lucky numbers 大水题

#include<stdio.h>#include<math.h>int main(){    int n;    __int64 m;    scanf("%d",&n);    m = pow(2,n+1) - 2;    printf("%I64d\n",m);    return 0;}#include<stdio.h>#include<math.h>int main(){    __int64 a[56];    int m,i;    a[0] = 0;    for(i = 1;i <= 55;i++)    a[i] = a[i-1] + pow(2,i);    scanf("%d",&m);    printf("%I64d\n",a[m]);    return 0;}