最短题解

#include <bits/stdc++.h>
using namespace std;
int a[10000005];
int main(){
int n,i,j,m;
cin >> a[1] >> a[2];
cin >> m >> n;
int s = a[1]+a[2];
for(i = 3; i <= n; i++){
a[i] = a[i-1]+a[i-2];
s = s + a[i];
if(a[i]>=m){
break;
}
}
cout << s;
return 0;
}