n = input()
a = [int(i) for i in n]
tmp = 0
cnt = 0
ans = 0
for i in a:
t = i % 3
tmp = (tmp + t) % 3
cnt += 1
if t == 0 or tmp == 0 or cnt == 3:
ans += 1
cnt = 0
tmp = 0
print(ans)#include<bits/stdc++.h>
using namespace std;
typedef long long ll;
const ll N=1e6+100;
const ll M=998244353;
ll dp[N][3];//第i位的余数为0，1，2；
int main() {
string s;
cin>>s;
ll ans=0,st=0;
dp[0][0]=dp[0][1]=dp[0][2]=0;
for(int i=0;i<s.size();i++)
{
ll zhi=(s[i]-'0')%3;
if(zhi==0)
{
dp[i][2]=dp[i][1]=dp[i][0]=0;
ans++;
}
else if(zhi==1)
{
if(dp[i-1][2])
{
dp[i][2]=dp[i][1]=dp[i][0]=0;
ans++;
}
else
{
if(dp[i-1][1])dp[i][2]=1;
else dp[i][2]=0;
dp[i][1]=1;
}
}
else if(zhi==2)
{
if(dp[i-1][1])
{
dp[i][2]=0;dp[i][1]=0;dp[i][0]=0;
ans++;
}
else
{
if(dp[i-1][2])dp[i][1]=1;
else dp[i][1]=dp[i-1][1];dp[i][2]=1;
}
}
}
cout<<ans<<endl;
return 0;
}
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305B - Continued Fractions | 1165B - Polycarp Training |
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1462B - Last Year's Substring | 1608B - Build the Permutation |
1505A - Is it rated - 2 | 169A - Chores |
765A - Neverending competitions | 1303A - Erasing Zeroes |