//10238.cpp #include <bits/stdc++.h> #define ll long long using namespace std; struct mon { float p;//dan jia float tt;//zhong liang float m;//zong jia }; int n,t;float cnt=0; bool cmp(mon x,mon y) { return x.p>y.p; } int main() { cin>>n>>t; mon s[n+5]; for(int i=0;i<n;i++) { cin>>s[i].tt>>s[i].m; s[i].p=s[i].m/s[i].tt; } sort(s,s+n,cmp); for(int i=0;i<n;i++) { if(s[i].tt<=t) { cnt+=s[i].m; t-=s[i].tt; } else { cnt+=s[i].p*t; break; } } printf("%.2f",cnt); return 0; }