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#include <cstdio>
#include <algorithm>
#include <cmath>
using namespace std;
#define EPS 0.000001
int main() {
int numLiquids, reqCon, liquid[101];
double sumSubst=0, sumLiquid=0, actCon;
fill(liquid,liquid+101,0);
scanf("%d%d",&numLiquids,&reqCon);
for (int i=0;i<numLiquids;i++) {
int con, amount;
scanf("%d%d",&con,&amount);
liquid[con]+=amount;
sumSubst+=(double)(amount*con)/100;
sumLiquid+=(double)amount;
}
if (sumLiquid==0) {
printf("0.000\n");
return 0;
}
actCon=(sumSubst/sumLiquid)*100;
for (int i=0;i<=100;i++) {
if ((actCon<(double)reqCon)&&(liquid[i]>0)) {
double perc=(double)i/100, toSub=(double)((double)reqCon*sumLiquid-100*sumSubst)/((double)reqCon-(double)100*perc);
toSub=min(toSub,(double)liquid[i]);
sumLiquid-=toSub;
sumSubst-=(toSub*i)/100;
}
if ((actCon>(double)reqCon)&&(liquid[100-i]>0)) {
double perc=(double)(100-i)/100, toSub=(double)((double)reqCon*sumLiquid-100*sumSubst)/((double)reqCon-(double)100*perc);
toSub=min(toSub,(double)liquid[100-i]);
sumLiquid-=toSub;
sumSubst-=(toSub*(100-i))/100;
}
if (sumLiquid==0) {
printf("0.000\n");
return 0;
}
actCon=(sumSubst/sumLiquid)*100;
if (fabs((double)reqCon-actCon)<EPS)
break;
}
printf("%.3lf\n",sumLiquid);
return 0;
}
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