#include<cstdio>
#include<iostream>
using namespace std;
long long n; //课的长度
long long m; //每次罚站消耗的体力
long long d; //每次罚站增加的注意力
long long a; //咖啡带来的体力
long long fazhan; //罚站次数
int sqzchu(long long a,long long b){
if(a%b==0) return a/b;
else return a/b+1;
}
int main(){
freopen("timeout.in","r",stdin);
freopen("timeout.out","w",stdout);
cin>>n>>m>>d>>a;
a+=100;
fazhan=sqzchu(100,d);
if(fazhan>n){
cout<<"N0";
return 0;
}
a-=fazhan*m;
if(a<0) cout<<"N0";
else cout<<a;
return 0;
}