Since 1800 is leap year as per Julian calendar. Day lies on

Solutions : 

#include <stdio.h>

// 

int main() {

    int n,leap=0;

    scanf("%d",&n);

    if(n%4==0)

        leap=1;

    if(n>1918)

    if(leap)

        if(n%100==0 && n%400!=0)

            printf("13.09.%d",n);

        else

            printf("12.09.%d",n);

    else

        printf("13.09.%d",n);

    if(n<1918){

        if(leap==0)

            printf("13.09.%d",n);

        else

            printf("12.09.%d",n);

    }

    if(n==1918)

        printf("26.09.%d",n);

 

    return 0;

}