#include<stdio.h>

int main(void) {
	char str[200000];
	int count = 0, ponnum = 0, painnum = 0;
	int cheak = 0;
	scanf("%s", str);
	for (int i = 0; i < (sizeof str -sizeof str[0]); i++) {
		if (cheak) {
			break;
		}
		switch (str[i]){
		case 'p':
			ponnum++;
			painnum++;
			break;
		case 'o':
			if (ponnum == 1) {
				ponnum++;
			}else {
				ponnum = 0;
			}
			painnum = 0;
			break;
		case 'n':
			if (painnum==3){
				cheak = 1;
			}
			if (ponnum == 2) {
				count++;
			}
			ponnum = painnum = 0;
			break;
		case 'a':
			if (painnum == 1) {
				painnum++;
			}
			else{
				painnum = 0;
			}
			ponnum = 0;
			break;
		case 'i':
			if (painnum == 2) {
				painnum++;
			}
			else {
				painnum = 0;
			}
			ponnum = 0;
			break;
		default:
			ponnum = painnum = 0;
			break;
		}
	}
	count--;
	if (count < 1 ||cheak == 0) {
		count = -1;
	}
	printf("%d", count);
}