#define _USE_MATH_DEFINES

#include <iostream>		//cin, cout
#include <vector>		//vector
#include <algorithm>	//sort,min,max,count
#include <string>		//string,getline, to_string
#include <cstdlib>		//abs(int)
#include <utility>		//swap, pair
#include <deque>		//deque
#include <climits>		//INT_MAX
#include <bitset>		//bitset
#include <cmath>		//sqrt, ceil. M_PI, pow, sin
#include <ios>			//fixed
#include <iomanip>		//setprecision
#include <sstream>		//stringstream
#include <numeric>		//gcd, assumlate
#include <random>		//randam_device
#include <limits>		//numeric_limits
#include <time.h>       //tm

using namespace std;
constexpr int64_t D_MOD = 1000000007;

int main() {

    int A, B, C, D, E;
    cin >> A >> B >> C >> D >> E;

    int amekazu = (B - C) * A;
    int sum = 0;
    int maeame = D, imaame;

    if (amekazu > 0) {
        sum = D;
    }

    for (int i = 2; i <= amekazu; i++) {
        if (i % 10 != 0) {
            imaame = maeame;
        }
        else if (i % 10 == 0 && E <= maeame) {
            imaame = maeame - E;
        }
        else {
            imaame = maeame;
        }
        sum += imaame;
        maeame = imaame;
    }

    cout << sum << endl;

    return 0;

}