#include<bits/stdc++.h>
using std::cin;
using std::cout;
using std::endl;
using ll = long long;
using std::vector;
#define rep(i,j,k) for(int i=int(j); i<int(k); i++)
#define REP(i,j,k) for(int i=int(j); i<=int(k); i++)


int main(){
    ll N, M, K; cin >> N >> M >> K;
    vector<vector<ll>> data(N);
    rep(i,0,M){
        ll index, val; cin >> index >> val;
        data[index-1].push_back(val);
    }
    ll sum = 0;
    vector<ll> val(N), now(N);
    bool flag = false;
    rep(i,0,N){
        sort(data[i].begin(), data[i].end());
        if(data[i].empty()){
            flag = true;
            now[i] = -1;
            continue;
        }
        now[i] = data[i].size()/2;
        val[i] = data[i][data[i].size()/2];
        sum += val[i];
    }
    if(sum <= K){
        if(false){
            bool mod2 = 1;
            while(sum < K){
                rep(i,0,N){
                    if(sum == K) break;
                    if(mod2 != data[i].size()%2) continue;
                    if(now[i] == data[i].size()-1){
                        val[i] += K-sum;
                        sum = K;
                        break;
                    }
                    if(K-sum <= data[i][now[i]+1]-data[i][now[i]]){
                        val[i] += K-sum;
                        sum = K;
                        break;
                    }
                    now[i]++;
                    val[i] = data[i][now[i]];
                    sum += data[i][now[i]]-data[i][now[i]-1];
                }
                mod2 ^= 1;
            }
        }
    }
    else{
        bool mod2 = 0;
        while(K < sum){
            rep(i,0,N){
                if(sum == K) break;
                if(now[i] == -1) continue;
                if(mod2 != data[i].size()%2) continue;
                ll wid = data[i][now[i]];
                if(0 < now[i]) wid -= data[i][now[i]-1];
                if(sum-K <= wid){
                    val[i] -= sum-K;
                    sum = K;
                    break;
                }
                now[i]--;
                val[i] -= wid;
                sum -= wid;
            }
            mod2 ^= 1;
        }
    }
    ll ans = 0;
    rep(i,0,N){
        for(auto p:data[i]){
            ans += std::abs(val[i]-p);
        }
    }
    cout << ans << endl;
}