/* 智商短路: dfs枚举 可以直接递推,和01背包一样的思想,哎,,智商着急啊! */ #include<iostream> #include<algorithm> #include<stdio.h> #include<string.h> #include<vector> using namespace std; typedef long long int ll; const ll mod = 998244353; const int maxn = 50; ll n,m,p[maxn+5],q[maxn+5],ans; ll poww(ll a,ll b) { ll ans=1,base=a; while(b!=0) { if(b&1!=0) ans=ans*base%mod; base=base*base%mod; b>>=1; } return ans%mod; } void dfs(int s,ll fz,ll fm,ll num) { if(s==m) { ans = (ans + fz*poww(fm,mod-2)%mod*n%mod*num%mod); return; } dfs(s+1,fz,fm,num); dfs(s+1,fz*(p[s]-1)%mod,fm*p[s]%mod,num*q[s]%mod); } int main() { int T; scanf("%d",&T); while(T--) { scanf("%d",&m); n = 1; for(int i=0; i<m; i++) { scanf("%I64d %I64d",&p[i],&q[i]); n = poww(p[i]%mod,q[i]) * n%mod; } ans = 0; //dfs(0,1,1,1); ll fz = 1, fm = 1; for(int i=0;i<m;i++) { fm = p[i]*fm%mod; fz = (fz*p[i]%mod + fz*(p[i]-1)%mod*q[i] )%mod; } ans = fz*poww(fm,mod-2)%mod*n%mod; printf("%I64d\n",ans); } return 0; }
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