递推题解

#include<stdio.h>

int rose[100010]={0,1};

int main(){
    for (int i=2;i<=40;i++) rose[i]=rose[i-1]*2;
    int m,n;
    scanf("%d%d",&m,&n);
    printf("%.7f",rose[n]*1.0/rose[m]);
    return 0;
}