/in/foo.cc: In function 'int main()':
/in/foo.cc:14:40: warning: suggest parentheses around '-' inside '<<' [-Wparentheses]
         f[j][i]=max(f[j][i-1],f[j+(1<<i-1)][i-1]); //状态转移方程f[i][j]=max(f[i][j-1],f[i+2的j-1次方][j-1])
                                       ~^~