新手求教改语法错误C?

Question

不太清楚语法哪里错了？

#include <stdio.h>
#include <string.h>

int n = 1000000;
int mark[1000001];
int N, M;
int c, i;
scanf("%d,%d", &N,&M);


int main() {
    int c;
    memset(mark, 0, sizeof(mark));
    mark[0] = 1;
    mark[1] = 1;

    for (c = 2; c * c <= n; c++) {
        if (mark[c] != 1) /*是待筛选的数*/
        {
            for (i = M; i <= n / c; M++)
            {
                mark[c * i] = 1;
            }

        }
    }

    if (mark[c] != 1)
    {
        printf("%d\n", c);
    }

    return 0;
}

Line 8: error: expected declaration specifiers or '...' before string constant
Line 8: error: expected declaration specifiers or '...' before '&' token
Line 8: error: expected declaration specifiers or '...' before '&' token
Line 8: warning: data definition has no type or storage class
Line 8: error: conflicting types for 'scanf'

Answer 1

int n = 1000000;
int mark[1000001];
int N, M;
int c, i;
scanf("%d,%d", &N,&M);

这一堆放到main函数里面