C言語の課題教えてくれ

#include <stdio.h>

int main(voi) {
____int i;
____int marks[100];
____int cnt70 = 0;
____int cnt50 = 0;
____int cnt00 = 0;

____for (i = 0; i < 100; i++) {
________scanf("%d", &marks[i]);
____}

____for (i = 0; i < 100; i++) {
________if (marks[i] >= 70) {
____________cnt70 += cnt70;
________}
________else if (marks[i] >= 50) {
____________cnt50 += cnt50;
________}
________else {
____________cnt00 += cnt00;
________}
____}

____printf(">= 70 : %d\n", cnt70);
____printf(">= 50 : %d\n", cnt50);
____printf("< 50 : %d\n", cnt00);

____return 0;
}