#include<bits\stdc++.h>usingnamespace std;constint N =5001;int t[N];double p[N];double dp[N][N];intmain(){int n, T;
cin >> n >> T;for(int i =1; i <= n ; i++){
cin >> p[i]>> t[i];
p[i]/=100;}
dp[0][0]=1;double ans =0;for(int i =1; i <= n ; i++){double sum =0, item, power =pow(1-p[i], t[i]-1);for(int j =1; j <= T ; j++){
sum = sum*(1-p[i])+dp[i-1][j-1]*p[i];if(j >= t[i]){
sum = sum-dp[i-1][j-t[i]]*p[i]*power;
item = sum+dp[i-1][j-t[i]]*power;}else{
item = sum;}
dp[i][j]+= item;
ans += dp[i][j];}}
cout <<setiosflags(ios::fixed)<<setprecision(9)<< ans << endl;return0;}