#include<bits/stdc++.h> using namespace std; using Int=long long; using Real=long double; template<class T,class S>inline bool chmin(T&A,S B){return(A>B?A=B,1:0);} template<class T,class S>inline bool chmax(T&A,S B){return(A<B?A=B,1:0);} #define REP(i,n)for(int i=0;i<(n);++i) #define REP1(i,n)for(int i=1;i<=(n);++i) #define ALL(x)begin(x),end(x) #define drop(x){cout<<(x)<<'\n';return;} int A,B,C,D,E,ans; void sol() { cin>>A>>B>>C>>D>>E; REP(i,A*(B-C)) { ans+=D; if((i+2)%10==0&&E<=D)D-=E; } cout<<ans<<"\n"; } int main() { ios::sync_with_stdio(false); cin.tie(nullptr); cout.tie(nullptr); cout<<fixed<<setprecision(16); int T=1; //cin>>T; while(T--)sol(); }