#include <iostream>
#include <list>
#include <vector>
#include <string>
#include <stdio.h>
#include <stdint.h>
#include <iomanip>
using namespace std;

using uint = unsigned int;
using ll = long long;

#define CIN( LL , A ) LL A; cin >> A 
#define GETLINE( A ) string A; getline( cin , A ) 
#define FOR_LL( VAR , INITIAL , FINAL_PLUS_ONE ) for( ll VAR = INITIAL ; VAR < FINAL_PLUS_ONE ; VAR ++ ) 
#define FOR_ITR( ARRAY , ITR , END ) for( auto ITR = ARRAY .begin() , END = ARRAY .end() ; ITR != END ; ITR ++ ) 
#define RETURN( LL , ANSWER ) const LL answer_for_contest = ( ANSWER ); cout << answer_for_contest << endl; return 0 

template <typename T> inline T Distance( const T& a , const ll& b ){ return a < b ? b - a : a - b; }

int main()
{

  CIN( ll , A );
  CIN( ll , B );
  CIN( ll , C );
  CIN( ll , D );
  CIN( ll , E );
  B = ( B - C ) * A + 1;
  ll answer = 0;
  FOR_LL( i , 1 , B ){
    if( i % 10 == 0 ){
      if( E <= D ){
	D -= E;
      }
    }
    answer += D;
  }
  RETURN( ll , answer );

}