会了的看看

重做的时候就G了

#include<bits/stdc++.h>
using namespace std;
int d[20],f[20] = {0};
int main()
{
	int a,n,m,x;
	cin >> a >> n >> m >> x;
	int up_bus = 0;
	while(f[n-1]!=m)
	{
		if(n<=2)
		{
			cout << a << endl;
			break;
		}
		d[1] = a;
		d[2] = up_bus;
		f[2] = a;
		for(int i = 3;i <= n;++i)
		{
			d[i] = d[i-1] + d[i-2];
			f[i] = d[i] + f[i-1] - d[i-1];
		}
		up_bus++;
	}
	cout << f[x] << endl;
	return 0;
}