#include <bits/stdc++.h>


using namespace std;

inline void Read( int & x ){
	x = 0;
	char ch;
	for( ch = getchar() ; ch < '0' || ch > '9' ; ch = getchar() );
	for( ; ch <= '9' && ch >= '0' ; ch = getchar() ) x = x * 10 + ch - '0';
} 

int main( int argc , char * argv[] ){
	//freopen( "Sample" , "r" , stdin );
	int p , d , m , s , ans = 0;
	cin >> p >> d >> m >> s;
	for(int i = 1 , j = p ; s >= j ; ++ ans , j = max( j - d , m ) ) s -= j;
	printf( "%d\n" , ans );
	return 0;
}