#include<iostream>
#include<vector>
#include<algorithm>
using namespace std;
typedef long long ll;
int main()
{
ll n; cin >> n;
vector<ll> a(n + 1, 0), dp(n + 1, 0);
for(ll i = 0; i < n; i++) cin >> a[i];
dp[0] = a[0]; dp[1] = a[1];
for(ll i = 2; i < n; i++) dp[i] = min(dp[i - 1], dp[i - 2]) + a[i];
cout << dp[n - 1];
return 0;
}
I2luY2x1ZGU8aW9zdHJlYW0+CiNpbmNsdWRlPHZlY3Rvcj4KI2luY2x1ZGU8YWxnb3JpdGhtPgp1c2luZyBuYW1lc3BhY2Ugc3RkOwp0eXBlZGVmIGxvbmcgbG9uZyBsbDsgCmludCBtYWluKCkgCnsKCWxsIG47IGNpbiA+PiBuOwoJdmVjdG9yPGxsPiBhKG4gKyAxLCAwKSwgZHAobiArIDEsIDApOwoJZm9yKGxsIGkgPSAwOyBpIDwgbjsgaSsrKSBjaW4gPj4gYVtpXTsKCWRwWzBdID0gYVswXTsgZHBbMV0gPSBhWzFdOwoJZm9yKGxsIGkgPSAyOyBpIDwgbjsgaSsrKSBkcFtpXSA9IG1pbihkcFtpIC0gMV0sIGRwW2kgLSAyXSkgKyBhW2ldOwoJY291dCA8PCBkcFtuIC0gMV07CglyZXR1cm4gMDsKfQ==