EDPCのJ問題，すしのやつ https://atcoder.jp/contests/dp/tasks/dp_j ```cpp double f(int s1,int s2,int s3){ if(seen[s1][s2][s3]) return dp[s1][s2][s3]; seen[s1][s2][s3]=true; double res=1; if(s1>0) res+=f(s1-1,s2,s3)*s1/n; if(s2>0) res+=f(s1+…