Codeforces 225E 梅森素数

Posted 2020-09-30 树的种子

注：梅森素数，数组表示的是2^n-1的n，指数。

#include <stdio.h>
#include <math.h>

const int maxn = 40;
const int MOD = 1e9+7;
typedef long long ll;


int a[45] = {2,3,5,7,13,17,19,31,61,89,107,127,521,607,1279,2203,2281,3217,4253,4423,9689,9941,11213,
             19937,21701,23209,44497,86243,110503,132049,216091,756839,859433,1257787,1398269,
               2976221,3021377,6972593,13466917,20996011};

int main(int argc, char const *argv[])
{
    int n;
    scanf("%d",&n);
    n--;
    int tmp = a[n];
    tmp--;

    ll ans = 1;
    for(int i=0;i<tmp;i++)
        ans = ans*2 %MOD;
    ans--;
    printf("%I64d\\n", ans);

    return 0;
}