题解

#include<iostream>
using namespace std;
int a,b,m,n,c[370];
int main(){
    cin>>a>>b>>m>>n;
    int sum=a+b;
    c[1]=a;
    c[2]=b;
    for(int i=3;i<=n;i++){
        c[i]=c[i-1]+c[i-2];
        sum+=c[i];
        if(c[i]>=m){
            break;
        }
    }
    cout<<sum;
    return 0;
}