题解

#include<iostream>
using namespace std;
int main(){
    int n,m,z,p[1010],k[100],sum=0;
    cin>>n>>m>>z;
    for(int i=1;i<=n;i++){
        cin>>p[i]>>k[i];
        sum+=p[i]*k[i];
    }
    if(sum>=m){
        cout<<sum;
    }else{
        cout<<sum+z;
    }
    return 0;
}