ZOJ 3171 The Hidden 7's

#include <iostream>
#include <memory.h>
#include <cstdio>
using namespace std;
const int maxn = 10001;
char str[maxn];
long long dp[6];
int main(){
while (~scanf("%s", str)){
memset(dp, 0, sizeof(dp));
int len = strlen(str);
for (int i = 0; i < len; ++i){
str[i] = tolower(str[i]);
if(str[i] == 's'){
dp[0]++;
}else if(str[i] == 'e'){
dp[1] += dp[0];
dp[3] += dp[2];
}else if(str[i] == 'v'){
dp[2] += dp[1];
}else if(str[i] == 'n'){
dp[4] += dp[3];
}
}
printf("%lld\n", dp[4]);
}
return 0;
}