#include <iostream>
using namespace std;
int main() {
int a,b,c,d,e=0,f=0;
cin>>a;
for(b=0;b<a;b++){
cin>>c>>d;
e+=c;
f+=d;
}
e-=e/10;
if(e>=f){
cout<<f;
}
else{
cout<<e;
}
return 0;
}
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